I'd suggest also to don't let AChat remember the passowrd until the security hole I've reported will not be fixed.
https://funnyadultgamesplay.com/forum/index.php/topic,2441.0.html
If they stolen your password probably the options are 3:
1. Your password was too easy to guess
2. Another account of some other site is been hacked
3. You have a malware in your PC
The point 1 is obvious, choose a better password!
The point 2 can be also fixed, just use different passwords for different accounts.
The point 3 can be easilly attenuated with my advice below.
For learn how to choose a good password please watch this video:
http://www.youtube.com/watch?v=0RCsHJfHL_4