hello.
I also have problems with this router.
Had version 5.20 (today upgraded to 5.21 and bootloader to v 3.0 we will see now)
It locks up almost every day in evening hours when trafic is high.
At first it just slows login procedure and then it stops open certain web pages and soon login becomes imposible for manual reboot not even over telnet.
then internet slows down more to nothing after about half hour after that watchdog reboots router. (thank god)
i looked at logs there is nothing.
We setup reboot of router in early morning for refreshing ram but that did not help.
wierd i have another same router same version on another interent connection and there is not any problems.
I have some indications that there is some very specific trafic to cause this lockup.
Sry for my english.