Hm, there is a way and its described here. However, I wouldn't recommend this. The firmware is very old (about two years) and the config system has changed a bit since that, so it may cause some problems. I've tested this on my router and it went well, but I suppose success would depend on the situation in this case.
I can try taking a look at your router's Troubleshoot file, maybe find a cause there. You can download the Troubleshoot file from the router's WebUI, System → Administration → Troubleshoot page.
Take note that the Troubleshoot file contains the router's configuration, so if you have any confidential info (like phone numbers) in the configs, I suggest removing them before uploading the Troubleshoot to a public forum.