Basically I am having the same problem as described in this thread .
My connection drops every time I want to search servers in the "Internet" tab but fine if I view servers in "History" or "Favorites" tabs.
Unfortunately my router may also suffer from the overflow problem (not sure how to check) and updating firmware/open ports doesn't help (buggy router known for having port forwarding problems)
So is there any way I could limit the amount of servers the steam client retrieve to prevent the overflow problem?