some DFS junctions does only work under XP but not W7


we have a NW 6.5SP7-Cluster with some cluster volumes. On one cluster volume there are some junctions to other volumes to give the user the ability to access there data over one drive letter.

All works under Windows XP. Under Windows 7 (64 bit) wt Novell Client 2 SP1 IR4 (32 bit) does only one junction work properly but not teh other two. All three target volumes are running on the same physical server, but on different virtual servers (cluster ressources). There is no difference in eDirectory rights or entrys in the volume or server objects what can explain the different working.
A new created junction to one of the not working targets does not working too (under Win7).

Where can I search for the cause? What can I do?