Firmware updates are really the only thing you can do, other than MAKING SURE that the router is getting clear power. If you have a UPS lying around, consider plugging the router into it for a week to see if things clear up.
Generally, this is not considered a great router. Here is a pretty good summary of what you'll find around the Internet:
The Linksys WRK54g is a Linksys wireless router (a stripped-down version of the Linksys WRT54G) bundled in the WKPC54G kit (which also contains a PCMCIA 802.11g card). It has been seen ranging the price tag of €150.
Unlike the Linksys WRT54G, however, it includes a Marvell-based chipset, only one antenna and is incompatible with the various firmware hacks available around. Actually, there's no sign of Linux in the firmware, only proprietary bits.
Considering the ever expanding possibilities of his full-fledged brother (which costs around €99) and the price of PCMCIA 802.11g cards dropping fast (around €50), this looks like a no-no.
-Warr