[ikthius]

Have you:
A: Cleared your cache/temp internet files.
B: Cleared your History
C: Cleared your files
D: Checked for spyware with AdAware/spybot/spyblaster/etc
E: Done a virus check.

try all these first, then, disconnect your modem for 3 mins+ then connect back up, then try your speed checks/pings

hope this helps.

ik