I set up a 64Bit Win7 Enterpreise on a MacBook Pro (Core2), and the HierarchicalSearch tasks are running fine so far.
Another difference (than what Bikeman mentioned) between the Apps ABP1 and S5R6 is that the latter uses a zip library that is pretty old and caused some trouble before.
If there really is no stderr.txt in the slot directory of that task (Computer\C:\ProgramData\BOINC\slots\0 or similar) please have a look there and see if there is a skygrid_* file in there and what its size is.
BM

Trouble with 'S5 all-sky GW' - WU
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I think the final solution would be to get rid of the 'switcher' completely and use the app_plan mechanism in the scheduler to deliver apps that match the CPU capabilities. First thing next year...
BM
BM