What programming language should I learn to manipulate and clean up data for analysis?

I would recommend either Python or Perl. Either one will serve you very well for that sort of task. Both are very powerful languages but are very different as well. Look up some examples on the net of the sort of tasks you will want to accomplish for both languages in order to get a feel for them, and then choose which one you feel more comfortable with. Coming from VB, Python may feel a little more natural to you, but both will be a change. Perl will probably make you feel a bit lost at first and will have a steeper learning curve.

I've used both of them for data analysis tasks myself, and typically do continue to use both. If you have the time to learn more than one language, it would not hurt you to learn both (plus, the more languages you learn, the easier it will be to learn a new one). You will find that some things are easier to do in Perl (text processing and filtering, due to its strong reliance on regular expressions, and quick and dirty one-time processing, due to its reliance on 'default' variables) and other things are easier to do in Python (restructuring and intermediate calculations, due to its large number of variable types and comprehension expressions).

R, a statistical language, may be worth looking at as well.