SigPlusNet Missing Module Exception

This dll is basically our interface to the signature pad itself and would fail with a FileNotFoundException. What was really strange was that the exception contained no information about the file it was trying to load. In addition, 95% of clients worked fine the first time. On the remaining 5% as soon as we started troubleshooting by installing Windows Updates or any other sample apps the error would simply go away.

After using a great little tool called FileMon (www.sysinternals.com) I found that the SigPlusNet.dll was failing on an attempt to find and load msvcr71.dll. Apparently msvcr71.dll is basically a set of C style application methods that are somehow used internally by SigPlusNet. Since this dll is pretty common it appears that on most machines it's installed by something else and so that's why on 95% of machines we had no issues.

Once I modified the install to include this dll, life is wonderful. A very strange unexpected dependancy...