Ahh, ok first of all this little trick may or may not work... type in 'null' as your password.
If it doesn't then you are going to have to do a factory reset on the phone using Sony Ericsson Update Service, downloadable from their support website. This will wipe your phones contents so I hope you have your contacts backed up or synced somewhere! When you start the phone back up one of the first things is to set you Gmail account up on the phone. You can reinstall any apps from the market.
Also if you have the option, don't use the pattern lock.... I answer so many threads on it because its caused the same sort of problem.
There is no security value to it as the person who may steal your phone only has to look around the forum to know that you can clear the phone off with the update service. The only thing it does is stop your nosy friends looking at the phone and then messing you right up when they input the pattern wrong. Sorry just my opinion! That said if you are with American AT&T you have to keep it.
Anyway let us know how you get on.