Well if it was your popup blocker a message at the top would appear saying it has blocked the popup. Try using another browser like Mozilla, or make sure you have the latest IE from the Microsoft update website. If these fail your computer might have a virus however ive never heard of a popup blocking virus
Try disabling your popup blocker under tools > Pop-up Blocker. Then goto this website http://javascript.internet.com/page-details/smart-popup.html a popup should appear.
If that doesnt work you could try scanning your computer for a virus I recommend TrendMicro Housecall its a free online virus scanner, which can be found at http://housecall.trendmicro.com/housecall/start_corp.asp
Well if either of these don't work for you i guess your going to have to read your private messages the old fashion way.

If that doesnt work you could try scanning your computer for a virus I recommend TrendMicro Housecall its a free online virus scanner, which can be found at http://housecall.trendmicro.com/housecall/start_corp.asp
Well if either of these don't work for you i guess your going to have to read your private messages the old fashion way.