I doubt it has anything to do with these
forums. If the problem was here, it would get widely reported immediately, and would probably be communicated to everyone, and fixed very quickly.
(I am experiencing no problems here.)
Your computer probably has some sort of malware infection which is giving you malicious pop-ups, twoard the goal of getting you to either spend
money on a sham virus detector / malware
removal program, or install additional malicious
software.
You should probably make sure your OS and anti-malware software is completely up to date, and do a compete scan.
If you are using windows, AVG is a very good, free malware / virus scanner:
AVG Free - Download Free Antivirus and Antispyware for Windows XP and Vista