I have the same router as you and it seems every month or two (Recently its been happening less) I get a high ping. In my case its not the ISP (I hooked up my laptop directly to the modem and the ping was normal). This is what I have done to get my ping back to normal:
1) Lower your MTU settings: When you access your router from your PC this should be on the main page. If its on auto switch it to manual. Then lower it to a lower number. I set mine to 1364 since I have an Xbox 360 and use Xbox Live, below this number I can't use Xbox Live.
2) I don't do this often and it doesn't always work but you could change your routers channel. Again access your router from your PC and look for the wireless tab, if memory serves me correctly it should be in the black bar. I use my router on Ch 11 now. According to Linksys the ping can be caused by environmental interference (i.e. wireless phones, etc).
3) The easiest thing to do it disconnect your power and let the router stay off for 1-2 minutes. In half the cases this solves the problem for me.
4) Update your firmware, when these problems first started for me I updated the firmware and this solved the problem for a month. It's possible your current firmware is outdated or corrupted.
5) The final option I can give you is to reset your router back to factory defaults. You will find a little depressed button on the back, get a pencil and hold it in for 30 seconds. This should reset the router back to its defaults.
After this the only other option I can give you is to use aftermarket firmware that I heard many people talk about. They say the Linksys firmware is crap and this fixes many of its problems. I would consider doing it but if you screw it up you might brick your router.
Just for a side note, I had the ping issue last night and I did everything I knew to do. I had to call Linksys and they told me about resetting the router back to factory defaults (#5) this worked but my ping when back up soon after. So I went into my router I put the channel back to 11 and set the MTU to manual and 1364 now my router works as intended and I played BF2142 for a half hour to make sure and I had no bad lagg.
If none of this works Linksys will offer to send you a new router. Personally I am worried that the once a month or two problem is going to get worse. Like I said last night when this happened my normal methods to fix the problem were not working. If re-setting my router doesn't work after that I am afraid they will give me a new router. Thats good but I hope its only the router and not the environment, but its weird how it isn't constant it only happens once every month or 2.
Please if anyone else has anymore input on the subject please tell me because this problem is very disturbing for me.
