I don't think I have anything particularly useful to add, others have
already suggested various ways to duplicate "evil power supply issues".
A few days ago someone on the list mentioned this device:
http://www.digilentinc.com/Products/Detail.cfm?NavPath=3D2,842,1018&Prod=3D=
ANALOG-DISCOVERY
which includes a D/A converter for generating wave forms as well as a scope
and logic analyzer. May be a suitable tool to help with the testing.

Personally, I've not seen this failure mode, though I can't say I've looked
particularly hard for it either.

But what I wanted to say is - thank you for a clear and well described
question. This should be pointed to in the FAQ as an example of how to ask
a good question.

-Denny
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