Latency issues, lag spikes

Hello,

I've been experiencing sporadic ping /latency for the past couple of weeks.  It is most noticeable in the evenings.  As far as I can tell it doesn't affect browsing too much, but it is very pronounced in online gaming where I get lag spikes every few seconds.  The latency would spike to 200-300 ms where normally it should sit around 70-80ms on a given server.  I've had friends test their connection on the same servers and they have a steady ping that doesn't vary by more than a few ms from the average.

Even on popular websites like google.com where I have an average ping of 11ms, I get spikes up to 50-60 ms every few sesconds. 

A continuous ping test in the command prompt  or http://pingtester.net/ confirms the latency spikes mentioned above.  A ping test using software from here http://www.speedtest.net/apps/windows shows a ping of 10ms and jitter of 15ms on a good day.  Sometimes it's much worse. 

Here is what I've tried so far.

- I connected my computer directly to the modem. 

- I tried different LAN cables. 

- Rebooted modem

- Hard reset the modem by holding the reset button for several seconds.  Interestingly this did not reset to factory settings, as the manual suggests.  It did not reset the password or the port settings, it just rebooted the modem. 

Modem: Business IP Gateway SMCD3G-CCR

Any suggestions would be appreciated. 

Thank you.