Guide data update problem

I have my TiVo connected to my router (I have broadband) so it should update automatically without my PC turned on or any prompting. TiVo Web says call scheduled for 12:00 Monday for example but it doesn't happen. The only way I can get it to update is to start my PC, go to TiVo Web and manually force the call. My XBox can get out to the web fine with the PC off so it should only need the router.

Also when I first set the TiVo up I could force the daily call from on the menus but can't anymore. I think this was because I was in Maintenance mode and a reboot since put it back in normal PAL mode. If this is why, is there a reason why you shouldn't leave the TiVo in maintenance mode?