I write in both c# and vb.net. They both use the .NET framework. Virtually all the built in classes are available to both languages. The capabilities are almost identical. The major differences are just syntax. If you can write a VB program, then you can write a C# program. It shouldn't take you very long to get comfortable with the either syntax.
To the best of my understanding, all the .NET languages are on a fairly even keel as far as what they can do, performance, etc. since they all get translated into the CRL before they actually get used.
I've found VB to be a much easier language to learn as the command names etc. are a little more english-like (not quite as english-like as COBOL , but I digress). Also, if you've done a lot of work in VB/VBScript you may find it easier to continue to use VB.NET.
However, if you are comming from a C++/Java type background you might find C# to be more to your liking.
But since I haven't done much in .NET since that seminar a couple of months ago, I'd take my advice with a grain of salt...
C# will translate better into any non-internet programming you will do.
Also, C# is recieving most of the attention both at Microsoft and outside and thus has more of a future. (There is some cool stuff coming down the pipe for future versions of C#)