TCP/IP half-open problem maybe?
I dont know if you already tweaked this, but feel free to increase your half-open connections limit by using this patch...
http://www.lvllord.de/
uTorrent by default uses 8 half-open connections and Windows limits half-open connections to 10, if you're getting somekind of error in your Windows logger (sorry I dont remember the programs name, I left XP a long time ago) you should try the patch.
The patcher is a small executable that has no interface but the one in the command line, you just need to type 'C' to change the amount of half-open connections then accept to patch the file, the patcher will copy a backup of the original file. If you're using SFC (most of windows users does, unless you heavily changed your XP installation) Windows will display a message telling you to insert XP cd to recover some system files (the patched one) just click "Cancel" then "No".
About the internet speed tweakers: I always looked before learning how to tweak connections with tweakers like SG TCP otimizer (
http://www.speedguide.net/downloads.php) but it never worked for me always bad results so I really dont recommend them.
And some important information...
Are you using firewall? What OS? It started to happen just now? Any antivirus trying to filter your http connections?
hmmmm well HELP 
