.NET 4.0 LDAP bind fails after patch install

Have a rather weird issue. Once .NET 4.0 framework patches are applied on a win2k3 box, the application running on it fails at the bind operation to AD. Specific error: System.DirectoryServices.DirectoryServicesCOMException(0x80005000): Unknown error (0x80005000) at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail) at System.DirectoryServices.DirectoryEntry.Bind()......

Performing a repair on the 4.0 framework and rebooting fixes the issue, but the next month when patches are applied it breaks again. During my research I have noticed that the most common cause of this is an OU with a / in it, but that is not the case here, and as I said, repairing the framework fixes the issue. Any ideas?