RSACryptoServiceProvider.VerifyHash() throws exception “Object identifier (OID) is unknown”

 

The problem occurs when calling RSACryptoServiceProvider.VerifyHash() in .Net 3.5.1. Only on some servers. Ok on windows 7 and most windows 2008 servers. But fails on 2003, where there is a hotfix that works (http://support.microsoft.com/hotfix/KBHotfix.aspx?kbnum=968730&kbln=en-us), but the problem also occurs on some 2008 Servers (Standard and Enterprise R2) with .Net 3.5.1 installed.

The exception we get is "Object identifier (OID) is unknown" when calling the VerifyHash() with the second parameter containing "SHA256".
rsa.VerifyHash(computedCheckSum, "SHA256", documentSeal)

This function call fails in some .net20 enviroments (2003 and some 2008 servers), but works in all .net40 envirmont:
if (!rsa.VerifyHash(computedCheckSum, "SHA256", documentSeal)){}

This one works in both .net2 and .net4:
if (!rsa.VerifyHash(computedCheckSum, CryptoConfig.MapNameToOID("SHA256"), documentSeal)){}