Linksys NSLU2 help needed

I've just bought a NSLU2 and it generally seems to work OK, but I'm having a slight difficulty with user groups permissions. Here's the story:

1) I have set up a share directory called 'projects' under Disk 1 (formatted at EXT3), then set up 'project1' and 'project2' share directories under 'project'.

2) I have given 'Group1' and 'Group2' read access to 'project'

3) Group1 has RW access to project1 and Group2 has RW access to project2

4) I have added myself as a user that is a member of Group1, but not Group2

5) If I use 'Add a New Network Place' or 'Map a Network Drive' to link directly to the 'project1' directory, I can access the folder as expected.

6) If I use the same process to link to 'project2', I am refused, as expected.

7)If I use the same process to link directly to the top level 'projects' share, I can see the two directories below it, but I can't have write access to either of them.

I want (7) to be the default setup because I'd like all users to see the top level share directory, but only have R or RW access to certain sub-folders.

Have I explained this clearly? Any suggestions? I am using Windows XP

Thanks

Simon