I've been having the exact same problem, but I don't have Vista. I have XP.
As I transcribe, if I stop typing for more than 2-3 seconds, the cursor jumps to the first position in the text box. This makes transcribing almost impossible because I'm constantly having to re-locate the cursor to where I actually want to be typing.
I don't use foot pedals or any other add-ons. I'm just using a regular installation of Express Scribe on a regular Windows XP computer. I'm using version 4.10 of Express Scribe.
Please help! Thanks!