That used to happen to me when I used Azureus and had too many torrents going at once (about 4 or 5). My connection used to drop periodically when I used Azureus too. I went back to Bittornado 3.18 (with max peer connections limited to 20) and now usually have 3 torrents going at once with no problems. Make sure you are using encryption and a port above 50,000 so your ISP doesn't throttle/interfere you.