[OpenAFS] weird access denied issues with windows client

[Christian]

All,

we are seeing some weird "access denied" issues with windows clients in 
our cell (iqo.uni-hannover.de). One example is openafs 1.7.13 64 bit. I 
have tokens, can access certain volumes using explorer, but others give 
me "permission denied", although I can access them under linux. 
Sometimes, I can access volumes under the RW tree, but not under the RO 
tree. This is always different from machine to machine. It does not only 
concern our cell, but also browsing other cells from our machines (e. g. 
desy.de). What could be wrong here? How can I best help debug this? Best,

Christian