I'm connected to KAD, but I can't search it.

I've started having this problem only recently, 3-4 days ago. It's driving me nuts, I don't understand what's going on....

It's weird, cause everything seems fine with KAD. I can download, the arrow on the little globe is green et cetera...but if I try searching, nothing comes up.

I've changed the UDP port (saw that on some message board) and now the search is working.

could of been your router doesn't like heavy UDP packets
or
your isp blocks ed2k default ports (low) i.e. 4662, 4672.

for reference mine are;
Standard TCP Port: 54662
Extended UDP port (Kad / global search): 54672
UDP port for server requests: 54665

i think its best to use above 50000 for these port, mainly beacuse other populaer applications use high port i.e. games, and if isps started blocking those, then gamers would move away.