Slow upload speed

[#1]

Hi all
I have been happily running with 5800-6000 kbps download speed on my conection (superb), but recently the plus net speed checker and various other speed testers have indicated that my upload speed is averaging around 36 kbps. This seems very slow considering my download speed is fine. I have gone through the standard fault ticket process with support and this has indicated no faults on the line. My line profile is at 7000 so the download speeds are sensible, but I cannot understand why with an upstream sync rate of 448kbps my upload speed is only clocking around 36kbps.
Can anyone help me sort out the upload speed issue as supposrt are now sugesting a visit from BT (which will probably cost me and I really don't believe this is a line fault sue to my perfectly fast download speeds).
Thanks

[#2]

Can you advise which security package you are running as it may be you have a rogue application running somewhere

[#3]

UPDATE - these results were on my PC connected by network cable to my Netgear wireless modem / router. If I run the same tests on my laptop downstairs (connected via wireless 802.11g to the router) I get downloads of 5411 kbps but UPLOADS of 353 kbps which is FINE. I'm now confused as this obviously isn't a router/splitter/line problem as only my PC suffers from the upload speed issue.
Both machines are running XP Pro Service Pack 3. I use ZoneAlarm free firewall on the laptop and ZoneAlarm Internet Security Suite on the PC. This would indicate to me that something on the PC is affecting my upload speeds.
Any suggestions gratefully received 

[#4]

It may be that your actual upload speeds aren't too bad but the Zone Alarm security suite is messing up the test.
Can you disable Zone Alarm and try again.
Is it possible to check the upload speed by uploading a file and timing it.