Available Updates for Remote Desktop Services (Terminal Services) in Windows Server 2008 R2http://support.microsoft.com/kb/2601888
Latest BaseCSP.DLL (as of April 2012):
You may wait for up to 30 seconds when you use a smart card to unlock a computer that is running Windows 7 or Windows Server 2008 R2http://support.microsoft.com/kb/2577550
Latest Winscard.dll (as of April 2012)
A program that requires you to use a smart card stops responding in a remote desktop connection in Windows Server 2008, in Windows Vista, in Windows 7 or in Windows Server 2008 R2http://support.microsoft.com/kb/2521923
...and make sure you're at SP1 on the W2k8 R2 terminal server....also make sure you create and set FilterCSPCardCacheByTSSessionConnectTime to 1 – it is by default 0 or not present (this is read by the BaseCSP.DLL component).
See also http://blogs.technet.com/b/instan/archive/2011/03/24/smartcard-redirection-diaries.aspx for other aspects.
Since KB2521923 has the latest version of Winscard.dll, will it also fix the problem specified in KB2424375?
Windows hotfixes are cumulative so if you have an LDR version of Winscard.dll nstalled (not a GDR version) that has a higher build number than a previous hotfix then that binary should contain all previous fixes to Winscard as well.