Latency increases to 500+ after a while on CS

I have an:

Intel 2.4 GHz Pentium 4 Processor
1G RAM
NVIDIA GeForce4 MX 420 Video Card

the problem is weird. I play counterstrike and my latency is fine, mainly below 70. Then after a while, the latency goes up to 500+. I haven't done anything to make this increase, except maybe log onto AIM. But after i exit AIM, the latency is still high. Maybe it is because of Norton? I have Norton AntiVirus 2k5. Is there any way i can lower the memory usage of all the processes?

Same thing happened to me yesterday. I tried restarting and everything but latency remained the same. Since i couldnt do anything, i went to sleep and went to school and when i came home, it was all good again. Then after a few hours it has the same problem again.

Is this from on line gamming with there server ? Probbly general internet lag depends on what tiem of the day you get on ? Also you can disable some of your services buy visiting www.blackviper.com this might also help you some ..

I dont think it is because of the server or time, because as of right now, the latency is still high. I tried blackviper.com, but it seems to be under construction.

If this helps, I use SBC Yahoo DSL.