I have the exact same problem as this guy, and i've also tried everything like him and I know my ISP don't block Limewire. So I'm going to suggest a possible Gnutella problem that only affects some people? (In my theory this may only affect Windows XP Home Edition SP2 users, my friend with his Mac on dial-up claims he has extremely abnormally fast downloads currently.)

All I can tell you is that I use Windows XP Home edition with Service Pack 2.

I had some trouble with the first 4.10 versions. Worked perfectly when I updated to v4.10.9 and ever since. I have been using v4.10.9 (both basic and Pro) , v4.12.3 Pro and now v4.12.6 Basic. This is also on two different computers with different hardware and setup, but with the same connection. The high CPU usage problem that I kept getting with the earlier versions were gone by v4.10.9

While I (through tests) believe the search might have some small bug (probably Java related. Hangs a bit sometimes) I have noticed no problems with connecting or downloading.

I BTW still have v4.9.37 on a different computer, and while it doesn't connect that easy anymore, when it finally connects, it is still as good as the new versions. Also same operating system on that one, but different hardware and some software.