I get a similar problem with my WRT54gc if I try to do a tracert from DOS. No solution to it yet (haven't spoken to Linksys about it yet - not a serious problem).
Is probably related to some specific thing you do / your computer does. If it is the computer, not easy to find out what it is (could be antivirus update, Windows Update, etc).
Check you have latest firmware, and try looking on the forums at
www.linksysinfo.org.