BlackBerry Browser (4.5) refuses to cache CSS. Is there a workaround?

I develop an internal web application for my company. It is used by our field technicians, all of whom carry a BlackBerry 8330 running 4.5. I would consider myself fortunate to have such a consistent target platform, if it wasn't BB 4.5...

I've noticed a lot of request overhead in loading the site, and know that if only my CSS resources were cached, the load time would be cut dramatically. The BB always requests a full copy of the CSS file, no matter if the Expires, Cache-Control, or Last-Modified headers are set. It doesn't hit its cache, it doesn't send an If-Modified-Since, nothing.

Anyone run into this or know what I can do to workaround it? I'd really like to avoid inlining my CSS if I don't have to.

EDIT: I just noticed that it is always requesting the page twice. Below are diffs between to 2 requests

GET /css/bb.css HTTP/1.1           |GET /css/bb.css HTTP/1.1
User-Agent: BlackBerry8330/4.5.0.77|User-Agent: BlackBerry8330/4.5.0.77
profile: http://www.blackberry.net/|profile: http://www.blackberry.net/
-----------------------------------|Accept: application/vnd.rim.html,te
-----------------------------------|Connection: close
Referer: http://10.7.2.167/page.php|Referer: http://10.7.2.167/page.php
-----------------------------------|Accept-Charset: ISO-8859-1,UTF-8,US
Host: 10.7.2.167                   |Host: 10.7.2.167
-----------------------------------|Accept-Language: en-US,en;q=0.5
-----------------------------------|x-wap-profile: "http://www.blackber
Cookie: PHPSESSID=xxxxxxxx; token=x|Cookie: PHPSES开发者_JAVA技巧SID=xxxxxxxx; token=x
-----------------------------------|Via: MDS_5.0.0.86

                                                                                                      |  
HTTP/1.1 200 OK                    |HTTP/1.1 200 OK
Date: Sun, 05 Sep 2010 09:34:52 GMT|Date: Sun, 05 Sep 2010 09:34:54 GMT
Server: Apache/2.2.15 (Debian)     |Server: Apache/2.2.15 (Debian)
Last-Modified: Sat, 04 Sep 2010 02:|Last-Modified: Sat, 04 Sep 2010 02:
ETag: "10426-d64-48f65ab39bf80"    |ETag: "10426-d64-48f65ab39bf80"
Accept-Ranges: bytes               |Accept-Ranges: bytes
Content-Length: 3428               |Content-Length: 3428
Cache-Control: max-age=12960000    |Cache-Control: max-age=12960000
Expires: Wed, 02 Feb 2011 09:34:52 |Expires: Wed, 02 Feb 2011 09:34:54
Vary: Accept-Encoding              |Vary: Accept-Encoding
-----------------------------------|Connection: close
Content-Type: text/css             |Content-Type: text/css