I am used to run emule ( ed2k/KAD P2P client ) behind VoIP router Linksys RTP300.
I have LAN connection 16/4 MBit/s.
I am aware about the router issue with full NAT translation table, so I restart it periodically.
But it does not always help.
Sometimes problem with traffic resists ( upload speed keps down, unstable connections ).
I have realized it often help to close and run again CFP.exe by closing tray icon,wait until close,
and run icon from desktop.
It looks like CFP gets tired by P2P traffic.
EDIT> BTW Closing CFP takes about 15-20 seconds when one core of Core2Duo E4600 2.6G is fully busy by that.
What is your experience ?