Cookies ??
 

Shad....

Every so often, when I log off and then later log back on.........the post that I have already read, show back up as "not read".

This happened again just now. After I "re-read" or opened the post again in one section. I logged off and then after 15 seconds, I logged back on.

Same post that I just opened.....were marked as Unread.

Is the site having a problem....or ....is it my computer?

Must be your computer. ;) You don't have to log off, though...it may be confusing your computer if you log off and back on within a short period of time.