1) You must choose a voicemail server (admin->system settings). This server handles statistics. If one is not chosen, some stats will be missing and some resets will not occur.
2) If your system is large, loading lists will bog it down too much. If you have more than 5 million "leads" in the system total, we have a "vicidial list archive" system which will allow you to archive/unarchive lists and improve performance.
3) Your best bet would be to contact The Vicidial Group directly (Vicidial.com has contact information). After them, of course ... PoundTeam is also good (wait! I work there! of course they're good!).
Happy Hunting