Hi Curt,
We've tried everything we can think of looking at the data, even starting with a new Excel worksheet containing no content from the original and still the problem exists.
What we ended up doing was re-recording our test and re-building the data driven portion of the test. This new one works fine with the full Excel file.
Weird.
I can only surmize that we did something in the original test that caused some odd interaction with Excel - given that it was a keyword test to begin with, I'm not sure how, but that is what happened.
For now I'm going to assume the problem is resolved and if we keep having a problem like this we'll open a support case.
Thanks.