Accessing external drive across network

I recently got a MacBook to replace my Toshiba WinXP machine. I use a Mini (running Tiger) with 3 external drives as a server, to which the laptop is backed up. The drives are accessed using Sharepoints. With XP I had no problems backing up and accessing the files as needed. With the MacBook I bumped into a variety of permission errors when I tried to access the files from the server. I finally checked "Ignore Ownership" and that seems to have made the files available, but I still get the do not enter icon on the directories. Clicking on the directory allows it to open, but it is annoying. My wife has the same problem, first with her ibook and now with her new MacBook. It causes problems with certain applications, as well.
Any help would be appreciated.

Thanks,
Anthony