Sometimes All Posts Shown As 'no Unread Posts'

i log on almost everyday

or at least 2 or 3 times a week

i simply go the the message board

about Thai visas

there i see a list of threads with all the topics

under that thread

and sometimes ALL of the topics are a lighter shade

indicating 'no unread posts'

this is quite odd

and makes it difficult to track where i have been,

what i have read, and what i need to read

when it shows ALL posts as having no unread posts even

the new posts i never saw before

i thought it might have to do with cookies, but it shouldn't

because it seems to me the Thai visa forum system keeps track of posts read on

their end

since i often have used Internet cafes and it didn't

matter what computer i used to see read and unread

posts

how can i fix this?

how can i keep this from happening?

is this clear?

does anyone else have this problem

thanks all