Hello heberstitcher,
We have scanned the site and know that there is no virus on the board itself, but there could be an issue with an ad. To help us solve this problem, could you answer a few questions:
1) What program is displaying the alert (ex. Norton Antivirus, McAffee, your internet browser)?
2) Could you post a screenshot of the warning next time it occur? You can post a screenshot by using the Print Screen button at the top right of your keyboard, then pasting into the reply. It would be useful to see both the warning itself and the ads that are on that particular page.