iPhone/Objective-C - Strange error when passing string to method

I am using http://www.sudzc.com/ to access SOAP Web Services in my iPhone application. I have a method in ASP.NET that takes a string and returns a string (facebook access token to be exact).

This string is the following:

iOCCeM4WGIwBlDxECRFr4AfIEsW598Z4sYjk2uMxsyo.eyJpdiI6IkZPQlN1YWlGNXY0aWs3SmFMWFUwcVEifQ.ITh3ZBGrbgU8DsYWz6d-S4Q1iNlQ8DwKGZB6RZvOkTUpa0VmW7qFS6MO1tkauHoJMFrOlwSrvVuMEO_SQTh8xtR2d0219PPSshiYBHYkjsokSYTuyIaSclVIrL2vh7xH

Every now and then I get an error like the following in my application and I'm not quite sure why. The actual string is a nvarchar(255) field within my database.

This error does not happen all the time. But it has happened quite a few times.

Any help would be greatly appreciated as to how I can fix this issue.

Thanks in advance.

Entity: line 20: parser error : AttValue: " or ' expected
            <span><H1>Server Error in '/' Application.<hr width=100% size=1 colo
                                                                ^
Entity: line 20: parser error : attributes construct error
            <span><H1>Server Error in '/' Application.<hr width=100% size=1 colo
                                                                ^
Entity: line 20: parser error : Couldn't find end of Start Tag hr line 20
            <span><H1>Server Error in '/' Application.<hr width=100% size=1 colo
                                                                ^
Entity: line 31: parser error : AttValue: " or ' expected
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 31: parser error : attributes construct error
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 31: parser error : Couldn't find end of Start Tag table line 31
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 46: parser error : Opening and ending tag mismatch: br line 29 and table
            </table>
                    ^
Entity: line 52: parser error : AttValue: " or ' expected
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 52: parser error : attributes construct error
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 52: parser error : Couldn't find end of Start Tag table line 52
            <table width=100% bgcolor="#ffffcc">
                         ^
Entity: line 67: parser error : Opening and ending tag mismatch: br line 50 and table
            </table>
                    ^
Entity: line 71: parser error : Opening and ending tag mismatch: br line 69 and body
    </body>
           ^
Entity: line 72: parser error : Opening and ending tag mismatch: br line 50 and html
</html>
       ^
Entity: line 73: parser error : Premature end of data in tag br line 48

^
Entity: line 73: parser error : Premature end of data in tag br line 29

^
Entity: line 73: parser error : Premature end of data in tag br line 27

^
Entity: line 73: parser error : Premature end of data in tag br line 27

^
Entity: line 73: parser error : Premature end of data in tag font line 24

^
Entity: line 73: parser error : Premature end of data in tag body line 18

^
Entity: line 73: parser error : Premature end of data in tag html line 1

^
2011-05-06 16:15:55.939 MyProject[9206:707] -[NSError AccessToken]: unrecognized selector sent to instance 0x4b87a10
2011-05-06 16:15:56.040 MyProject[9206:707] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSError AccessToken]: unrecognized selector sent to instance 0x4b87a10'
*** Call stack at first throw:
(
    0   CoreFoundation                      0x3237064f __exceptionPreprocess + 114
    1   libobjc.A.dylib                     0x365b3c5d objc_exception_throw + 24
    2   CoreFoundation                      0x323741bf -[NSObject(NSObject) doesNotRecognizeSelector:] + 102
    3   CoreFoundation                      0x32373649 ___forwarding___ + 508
    4   CoreFoundation                      0x322ea180 _CF_forwarding_prep_0 + 48
    5   MyProject                           0x000093ab -[MyAccountVC handlerGetUserByAccessToken:] + 46
    6   CoreFoundation                      0x322ddf03 -[NSObject(NSObject) performSelector:withObject:] + 22
    7   MyProject                           0x00026309 -[SoapRequest handleError:] + 148
    8   MyProject                           0x00026737 -[SoapRequest connectionDidF开发者_C百科inishLoading:] + 254
    9   Foundation                          0x31f4a2f5 -[NSURLConnection(NSURLConnectionReallyInternal) sendDidFinishLoading] + 68
    10  Foundation                          0x31f4a277 _NSURLConnectionDidFinishLoading + 78
    11  CFNetwork                           0x35e71411 _ZN19URLConnectionClient23_clientDidFinishLoadingEPNS_26ClientConnectionEventQueueE + 136
    12  CFNetwork                           0x35e65f49 _ZN19URLConnectionClient26ClientConnectionEventQueue33processAllEventsAndConsumePayloadEP20XConnectionEventInfoI12XClientEvent18XClientEventParamsEl + 100
    13  CFNetwork                           0x35e65e3b _ZN19URLConnectionClient13processEventsEv + 70
    14  CFNetwork                           0x35e65ded _ZN13URLConnection24multiplexerClientPerformEP18RunLoopMultiplexer + 36
    15  CFNetwork                           0x35e65d5f _ZN17MultiplexerSource7performEv + 126
    16  CFNetwork                           0x35e65cdd _ZN17MultiplexerSource8_performEPv + 8
    17  CoreFoundation                      0x32347a79 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 12
    18  CoreFoundation                      0x3234975f __CFRunLoopDoSources0 + 382
    19  CoreFoundation                      0x3234a4eb __CFRunLoopRun + 230
    20  CoreFoundation                      0x322daec3 CFRunLoopRunSpecific + 230
    21  CoreFoundation                      0x322dadcb CFRunLoopRunInMode + 58
    22  GraphicsServices                    0x3058241f GSEventRunModal + 114
    23  GraphicsServices                    0x305824cb GSEventRun + 62
    24  UIKit                               0x35550d69 -[UIApplication _run] + 404
    25  UIKit                               0x3554e807 UIApplicationMain + 670
    26  MyProject                           0x00003f73 main + 70
    27  MyProject                           0x00003f28 start + 40
)
terminate called after throwing an instance of 'NSException'
Program received signal:  “SIGABRT”.

Looks like my web service is down and I'm simply not handling it properly in Objective-C. Hence why it's returning HTML (ASP.NET error page) instead of the string.