Hi suchin,
I've moved your thread to the PainterFactory Help forum since it's more appropriate here.
I had a similar problem the other day, also using Firefox which had been working since I first joined back in July 2007. I could not log in and when I created a new account, my new password never arrived.
It turned out that all I needed to do was (in Firefox) go to Tools > Options > Privacy tab, click the Show Cookies button, scroll down and delete the painterfactory.com cookies. Next time I came to The PainterFactory, I was able to log in using my original user name and password, just like before. A new set of painterfactory.com cookies was automatically created.
Another member had the same problem, applied the same solution, and it worked for him too.
You might try that and see if it helps.
Good luck!