i guess there is a setting in firefox and chrome and i think the latest version of IE that allows you to use ggogle or other MALWARE lists for suspicios sites...
this is basically a redundant step and not usually very effective compared to your onsite virus detection system...
the blacklist sites like google are usually bad as they take days/weeks to update them, in other words they wont know it is a bad site until they or rather thier robots visit the sites...
you could be there before then, or in this case after the problem and it takes google weeks to remove sites form that list, and those lists pickup false positiives...
you can turn this 'feature' off in each browser in the security setting/option
i HAVE run all my GOOGLE webmaster tools and they are unable to ID any problem or malware on my sites....
I HAVE contacted google to have them take my site off thier blacklist, but according to thier info, it can take WEEKS for thyisto be reviewed for reconsideration