Try what I told you. It might be that the IDE bus is blocked while a write command is active, so no data can be read from the partition. This is even more probable with the drives being on different channels of the IDEfix adapter, because the read and write commands have to be finished before the IDEfix software can switch to the other channel. You should try to connect both devices as master and slave to the same channel.
The IDEfix adapter is not the same as the two disjunctive IDE controllers on a PC motherboard. The IDEfix only allows one IDE controller to be switched between two cables. But you can access only one cable at a time. If you read the manual of the IDEfix adapter, you'll see that you should first fill the first channel with a master and a slave before you use the second channel to connect a third and fourth device.
Bye,
Thomas