Mounted USB-drive does not work

[Levatos]

Hi,
I yesterday managed to mount a few drives which are attached to my PC on my notebook with nfs-server.
It's the drive where ubuntu is installed on my PC, another SATA-drive and two USB-drives, all attached to the PC.
At the beginning I could access all of them, after a while I had some troubles (do not remember which drives were unaccessable) but then it worked again (did not change anything - on purpose).
Now again I can't connect to either of those two USB-drives.
They are properly mounted but when I try to open them, e.g. with $ cd /mounteddrive it won't stop loading.
There is no error or anything. Same thing with nautlis.

Suggestions?