It shouldn't - I'm pretty sure that "Mark forum read" will update your read stats with the current time WHEN you click on the link. Perhaps you need to refresh your cache next time you visit the forum?
Next time you're in a forum, check the clock on the upper right - if it's not your current time (assuming you've properly set your time zone), refresh the page and see if things look a bit different.
If you keep having problems, send me a private message or email.
Should those images next to each thread disappear after you view the thread? Or do I have to do something to erase them on each forum? I could also just be talking out of my ass so whatever the case, help!