Error: Element not in cache

Hejhej,

when I try to upload a file into a shared folder I get this error message: "Transaktion153 fehlgeschlagen. ... Element is not in cache, [some numbers]". The folder is set on "shared with all and future friends". Uploading the same file into a privat or public folder and then copy it into the shared folder works fine.
I'm running Build 426 on WinXP SP2.

This problem is probably similar to:
http://getsatisfaction.com/wuala/topi...