Razorback 2 is up at the moment.
What has changed on your computer?
New firewall?
XP service pack 2?
A quick search of the emule forums suggests;
reducing the max number of connections and the connections per 5 seconds limit.
This may be due to one of those "internet accelerator" programs.
Screwed TCP/IP settings
Seems unlikly to be ISP blocking to me, they would do a better job of it.