k2 2.5.4, joomla 1.5.22, hostgator linux hosting account

when i click on items of one of the k2 categories, i receive the "404 article not found" error. all other categories/items work except this one. when i move items from that category into another one, those items work as well.

i'm not aware of any changes made to the site that would cause one category's items to no longer work correctly.

does anyone have any info or suggestions on this issue?

thanks!!