Office 2000 closing down

I run a medium network of approx 50 pcs all running NT4 sp6a. We have a unix server, a pdc and 2 bdcs running NT 4 server sp6a. Recently we purchased some laptops and have Windows 2000 sp1 on them. All workstations and the laptops have almost identical programs on them, including Office 2000 sp2. The one difference is that the laptops have PC Guardian 6.1.160 for encryption. My problem is this: the staff who use the laptops cannot use office 2000 when logged on to the domain or logged on locally with their normal user rights. When they open an office file or attachment the program begins to open then closes before it can display the file. Office works fine logged on as an administrator. Is this a registry permissions issue? How can I fix this?