I think, though not 100% sure, that the net statements used to map drives, and clear persistent mappings don't work properly with W98 as a rule. Mainly because the local profile which is launched AFTER the batch files from netlogon takes precedence.
If you are using W2K as your Domain Controller, and Active Directory, you might try uisng the profile GPO. Here you can set it up to not allow the client to implement its policy over the Domain policy. Though I'm not 100% sure (never am really!) if this works with W98 for the same reason, and only works with W2K Pro or above.
Can't hurt to try, though.
Will