I believe I have found a bug in the OpenCL driver library for linux. I get a segmentation fault (sometimes) when calling wait for events across several GPU's and driver versions.
I have made a small example program that triggers the bug. I have attached it (amdbug.cpp). Reversing the order of the two events (line 71 & 72) makes the program run without problem.
Hope this helps tracking down the bug.
I look forward to hearing from you.