Limewire has worked perfectly fine for me since I first downloaded it, but this morning I tried to open it, and it came up with the 'select language' then a wizard to 'help me optimise performance'. This had never happened before, so I just clicked cancel. Now it doesn't even reach the loading screen... I just double click the icon and nothing happens, though a process is open in the task manager. I tried reinstalling Java and both limewire pro and basic, and it still does the same thing... Someone help?

Try deleting LW's preferences folder when LW's closed (check in task manager & end the process if it's running). See points 2 & 3 below. If you've used older versions of LW, you could have a folder in either location - so check both.
Fixes for LimeWire

Also try changing compatibility to Win NT or 2000 (point 5 above).

I've never seen an optimisation wizard for LW Did you get your version from www.limewire.com ??

Ok I think it's all good now... I neglected to uninstall my older version of java before downloading the new one, and though doing so caused my computer to have its second critical error in its lifetime, of which I don't know how to fix apart from flicking off the power, limewire has decided to work again. Thanks for your help anyhow, if it happens again I'll try your advice.

And yes, I did get my original Basic version from Limewire.com, not my pro version however... that I got through my *********. But this error caused me to go back to basic anyway.

Just be wary of any programs you download from LW. Many are infected & many are screwed up & won't work as expected.
WARNING: Viruses on the network you should be aware of

Most of us see the cost of Pro more as a donation towards the future development of LW. It's a small expense for such a good app.

Mm yes I know, I once tried to download a dvd shrink-like program, and though I thought the size was reasonable, and though I scanned the zip before I extracted it, I got a virus that infected all of my norton quarantine files, so screwed my protection. Lesson = learned.

The only program I have ever paid for is Norton Antivirus... due to my beliefs that if I'm committing illegal activity and getting it all free, might as well go the whole nine yards...