Malware on site?

I found this
http://www.uphaa.com/blog/index.php/unfortunate-ironic-t-shirts/
and posted it on a blog. Someone posted a reply that the site was flagged by their software as dangerous and might steal personal information.
I had been there a couple of times without any warning, and I use Sunbelt's firewall which is usually pretty good. But I did notice that yesterday (Saturday) morning my keyboard began reversing upper and lower case letters and giving me symbols instead of numerals. The problem resolved itself in a minute or two and I thought I’d just hit one of those rare key combinations and created the problem myself. But I went back after reading friend’s warning and very quickly the screwiness returned and got worse.
Restarting the machine fixed the problem, although I've run a scan to be sure. No problems found. Nobody else has come back with anything similar.
Given that I can't connect the problems to the first few views, I'd like to know: is it possible for bugs to creep in progressively? Can they be structured so that repeat visits are needed for the malware to be fully transferred?