System.Security.Permissions.FileIOPermission

[paul]

I just installed Windows XP SP2 on my web server.
Now when I run one of the web applications I get the following error:

ArgumentException: Illegal characters in path.]

System.Security.Permissions.FileIOPermission.HasIl legalCharacters(String[]
str) +276

System.Security.Permissions.FileIOPermission.AddPa thList(FileIOPermissionAccess
access, String[] pathListOrig, Boolean checkForDuplicates, Boolean
needFullPath, Boolean copyPathList) +88
System.Security.Permissions.FileIOPermission..ctor (FileIOPermissionAccess
access, String path) +66
System.Windows.Forms.Application.get_StartupPath() +167

This happens when I call the following line of code:

Application.StartupPath

The correct value should be 'C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322'.

which appears fine on a non-xp sp2 machine. the function writes to a file
on the web server.
Any ideas, it must be some sort of file access setting that was 'enabled'
before the SP but can't find any help on MS support.

Any help is greatly appreciated.
thanks

paul