Exactly same happens to mine, drops connection for 30 sek, and gets back online by itself, sometimes it happens 5 times within 20 min other times it can be hours between.
Doesent seem to be any specific stuff triggering it, it can happen when browsing only or playing wow only - and then again sometimes it can run firefox utorrent and play wow at the same time without any problem.
Funny thing is the wireless stays online its only the cable lines that drops!?
Ive tryed 2 different ISP both PPPoE 3 different modems in bridged mode same drill...
ive updated the firmware a few times without any luck on solving this issue. So atm. im using the standard router thingie that goes with my ISP whitch arent really any hit, but it keeps me online:)
Anyone tryed the same and found a way to work around this?