Before anything else, login to Gmail now and check your filters and POP Forwarding settings and make sure there aren't any strange filters or e-mail address you don't recognize.
I read an incredibly alarming item from digg today about how an unscrupulous hacker stole someone's domain name by hacking into the person's gmail account.
David Airey, the victim, tells his story and the on-going saga to get his domain back in this blog post. If you're a freelancer, your website is your life, I can just imagine the emotional distress he is in.
According to the blog post, Google has already fixed this but the fix will NOT remove filters or settings that have been added or changed by the exploit, so I say again, check your Gmail account now.
Details of the hack can be found in http://www.gnucitizen.org/blog/google-gmail-e-mail-hijack-technique/