Bin dabei

Ok, in english now...
It seems that the card is definitely too slow. There is a SD speed test thread (actually, there are two) and the one guy has about 7.5mb/s read speed and 6.5mb/s write speed with his 150x 4gb Transcend card. This is a limit of the device, not of the card. I doubt if any card could reach significant higher transfer rates, because the n800 seems to be the bottleneck right now.
Have you tried to change the slot? Move it to the external slot and find out what happens. You can use dmesg to check if something is very wrong.
1mb/s transfer rate is not normal. I will receive my transcend card tomorrow (I hope so) and I am going to do a complete check, then I will report.
I hope this time it was no "Griff ins Klo".