Worry not, we'll try to help you out as best we can.
1) Okay, the first and easiest way of getting rid of this error message is to try and do a soft reset on your iPod. Press and hold Menu and the middle Select button down until the Apple logo appears. Then wait, and the iPod reboots. When you connect up to your computer now, the error message should no longer appear.
2) However, as you have noticed, once iPod enters deep sleep (after 36 hrs of inactivity), the error message will most likely reoccur, so restoring to a previous version (3.0.1) of the iPod firmware (the software than runs iPod) is the way to permanently fix your error. If you check your iPod go to Settings, About - and see what version of software you have in there. If it is 3.0.2 then it is likely your error is being cause by this buggy firmware we've been discussing.
3) If you have a new iPod, then it's likely you had this 3.0.2 firmware installed and shipped with your iPod. So you'll have to get in touch with David Robertson on this board to get him to email you the older updater. It's no longer available for download from Apple's Download site - so David is currently the sole hope for those who need the older version of updater.
4) If you get hold of this updater, you'll need to install it on your computer, connect your iPod, and select Restore - which will wipe your iPod, and put the 3.0.1 firmware on it. Be aware that all the music and data on your iPod will be lost - but fear not, if you have it all in iTunes, you can resynchronise your iPod and everything gets transferred back on again.
5) If you'd rather not bother with doing this - and would prefer to wait for Apple to solve the problem, you can do the soft reset thing I've suggested in 1) every time you see the error message. Or alternatively, use iPod frequently, so it doesn't have the opportunity to lose its settings after 36 hrs of inactivity.
I hope this helps you out. Don't be afraid if you need further help - post back if you need clarification or want more assistance. There are plenty of experts out here who can give you a hand...
Kind regards,
Da Gopha.