Experiencing extreme fluctuations in ping time and fps.

For the past 5 days, i have been experience extreme ping time and fps fluctuations which occur every 5 minutes. SL runs normally for 5 minutes then ping time goes through the roof and my fps drops to 2. This will last a few minutes then it gets to normal again. This will continue for as long as I am on SL. This is very frustrating:/ I never had this problem before, i dont have any virus on my computer, my cable internet connection is very good so I am at a loss with this very. I live in Montreal, Canada.
Could this be an SL issue, if not what can I do to fix this. I have tried lowering my graphics to low but i have the exact same situation. Please help!!!

I think it's SL itself. Although I have not experienced severe FPS drops, I have noticed frequent, almost regular ping spikes, packet loss going through the roof, and all the other signs of a network infrastructure on the verge of collapse. I know it's neither my computer nor my own internet connection, because I generally enjoy a good low-latency connection averaging 4.5Mb/s down / 522kb/s up. Oddly enough, these lag spikes seem at their worst after midnight, when traffic around my area is lightest.