If you are getting mysql error on the php pages, that means at least everything is "almost" working. =) Thankfully, mysql error has little to do with litespeed.
Since you mentioned that you didn't change the mysql server or config files for wordpress, and it was working before the move to litespeed, I'm a bit stumped.
Finding out the exact mysql error code is the next step. Are you getting authentication error or can't connect to mysql error? PHP should spit those out to the error logs at logs/stderr.log or logs/error.log under the lsws install.
Check wordpress config to see if your connection mysql through TCP or UNIX domain socket. If it is the later, PHP and the user running it, must have permission for that socket file location.
I would just double check the user/password combo for mysql in the wordpress file by going "mysql -umyuser -pmypassword" and see if you connect.
Reinstalling lsws wouldn't help since this is no longer a lsws issue but a php/mysql config one.