No, removing the main battery should not require a hard reset when you try to turn the Axim back on. If this were the case, the main battery should never have been easily replaceable.
In any event, I think this issue is directly related to the first issue you posted about
: your internal (or backup) battery is most likely dead. The backup battery, a little CRxxxx button sized I think, allows the Axim to go into 'sleep' mode when the main battery is disconnected. Since your backup battery seems to be dead, anytime you remove the main battery, your Axim's RAM cannot be powered whatsoever and poof(!), your data is lost.
If you haven't already, I would search the forums here for some variation of "replacing backup battery" to help solve your problems. Good luck.