Hey guys, i've managed to get a good dump with Progskeet 1.2 and the NAND clip. I had to use the first Bitstream (i think it was released October 21st). I plugged in the Progskeet while the switch on the Slave board was "on" (the LED on). Then turn the switch off and start WinSkeet. Now the NAND gets recognized correctly and i could dump successfully.
Maybe it is only my case that i couldn't dump with the newer Bitstreams, but i just wanted to share my experiences.