Invalid Cast Exception calling SqlMembershipProvider GetUser

I am implementing authorisation on a web application using the ASP.NET SqlMembershipProvider, but it is randomly throwing an invalid cast exception when calling the GetUser method.

I can log in, and navigate the pages all fine, but than at random points, boom, it craps out, and throws the exception:

Unable to cast object of type 'System.Int32' to type 'System.String'

Looking at the stack trace you can clearly see it is being caused by t开发者_运维知识库he Membership Provider:

[InvalidCastException: Unable to cast object of type 'System.Int32' to type 'System.String'.]
   System.Data.SqlClient.SqlBuffer.get_String() +5002910
   System.Data.SqlClient.SqlDataReader.GetString(Int32 i) +55
   System.Web.Security.SqlMembershipProvider.GetUser(String username, Boolean userIsOnline) +1169
   System.Web.Security.Membership.GetUser(String username, Boolean userIsOnline) +63
   System.Web.Security.Membership.GetUser() +19
   _Default.LoadLeadOverview() in \\file1\default.aspx.vb:169
   _Default.Page_Load(Object sender, EventArgs e) in \\file1\default.aspx.vb:30
   System.Web.UI.Control.OnLoad(EventArgs e) +91
   System.Web.UI.Control.LoadRecursive() +74
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2207

I have had a look around and found other people with the same issue, but no solution. Any thoughts would be welcome.

Whilst I haven't done anything to specifically resolve this issue, I haven't seen it in a couple of weeks. Looking back, I was testing the site in multiple browsers at the same time, with the same account, logging in and out a lot, and that seemed to be when then problem came up. Now all the CSS and other cross-browser stuff has been settled, I'm not using multi browsers so heavily, and not at the same time and it seems to be fine.

Is it possible some of your users have all digits as their username? It might be that auto type is boxing wrong somewhere along the way.