I spent sometime trying to solve the issue with a Cisco support analyst. It turns out that this is a known issue for these routers and the only solution is a firmware upgrade. According to the analyst, this upgrade was not going to be available anytime soon... I got the impression that he meant "never." My guess is that since this is a small business product without the juicy price-tag of high-end devices, Cisco does not care enough to solve the issue.
By the way, these routes have a one-year warranty, so Cisco support will try to help you if you call... my talk with them was about six months ago, maybe there has been progress since then.
