von Beethoven?

[Krelian]

I'm about 85% certain that "van" is just "von" conjugated differently.

Nope. "von" doesn't change its form ever. "van" is just a Dutch word.

EDIT: I've just wiki'd some info and I found that "von" was used only by the nobility at that time. So I am now certain that when he became famous, he changed his name from a commoner's to a nobleman's by the simple change of a letter.

He didn't change his name, though. It's "van Beethoven", it never was "von Beethoven".