If I try to run clAmdFftEnqueueTransform a second time I get a segmentation fault when using the CPU (Intel i7). There is no problem doing so when using a HD6770. This problem only occurs for fftSize=1e4 or bigger. For smaller FFT sizes both devices (GPU and CPU) run just fine with multiple FFTs in series (i.e. in a for-loop).
I can't figure out the problem.