Many of these issues seem to be appearing with old OSs as well, i.e.: WinME,Vista, and especially XP. In another thread there are several reports of users suddenly getting blank white pages and/or blank pages with just the header with non-functioning icons showing. I have a Mod who is still using XP and - no matter which browser she uses - she cannot get on the forum. The only thing she can do at the moment is read and reply by email. 
She said this started this past Monday. For a forum in Russia it began last Saturday. So, you should look at what OSs those that are having problems accessing your forums also. Just a thought…