A weird one this ......
We use WSS 3.0 a lot here, and recently we came across a problem which was a bit odd and we couldn't work out if this was a real problem or some kind of permissions problem.
Basically someone had created a view within sharepoint which included some colums in which the fields were set as Multiple Values
When the page was edited in Datasheet view, these fields were no longer visible!
Change the page back to normal and they are back again
Other users could see these fields when they were in datasheet view so we knew it was possible
Anyway, the resolution was to install this
The clients were Windows XP SP3 and Office 2003 SP3 using IE8