internet speed drops off drastically

I had put up a post earlier about my audio breaking up whenever I have been
on the internet for awhile streaming videos from youtube or news web sites.
Also, when downloading music from Rhapsody. I have a 10 Mbps internet speed
, 4GB Ram and a quad core intel processor. I did a random test of internet
speed today and saw I was only getting 3.5 Mbps. The Isp provider had me
disconnect my DSL modem and router and then reconnect but that did not fix
the problem. However, as soon as I rebooted and di the speed test and it was
back up over 10 Mbps. Rebooting also gets my audio and internet speed back
where it belongs. Has anyone else run into this problem and found a fix.

I googled this issue and found several other people who were experiencing
this same issue but noone had come up with a solution.

The next time this happens I will test the bandwith speed on my XP laptop to
see if it is down along with my Vista desktop. I haden't done that before to
see if it is a problem on both machines at same time or if it is specific to
the vista system.

How do you get 10Mbps via DSL? You probably meant cable. DSL is typically
several times slower than Coax cable and why bother with such outdated
protocol.
And what is it DOWNlink or UPlink? I bet 10Mbps is your downlink, uplink is
several times slower, and on DSL like 10x slower.

Something is strange here.
Wait fo rmore response but this i smy reaction - DSL can't provide you with
10Mbps.