PokerTracker

I played a bunch on FTP over Christmas/January and changed the setting in PT3 to set the mine username setting to my FTP username, I now which to change back to my stars name, and I can't seem to do it. Every time I load the setting tab and click to change the mine category as before it just spends 5-10mins loading the list of usernames and then crashes. If I filter it to pokerstars only it crashes almost instantly - as does searching for my username. Is there a way I can change this setting manually?

You could via a direct database query, but what might be easier is just aliasing your two names together - you'll also get all of your results combined as an added bonus. See the Tutorial: Aliases for a walkthrough on how to use this functionality.

I'm not sure you understand, as soon as I try to use the "find a player" dialogue box at all it freezes and crashes.

What version of PT3 are you using? Check the title bar of PT3 - if it isn't one of the current versions please update:
Download page
PT3 Build History / Release Notes

If you see the problem in one of the current versions please report your problem so that we can investigate further.

it was the latest beta. I deleted the database and should now be able to fix it.