BuddyPress.org

Dennyhalim.com-

so it seems that bp cannot correctly calculate the time the blog last active.

this might related to timezone problem.

This thread shows you how to deal with this issue: https://buddypress.org/forums/topic.php?id=2437#post-13341

i check between the blog that cause problem and the blog listed before it,

all have same plugin activated.

So, if you do not have any plugins activated anywhere, except BuddyPress, you still have this issue?