Just an update: I've found the exact change which causes this issue. I changed a formula to approximate the inverse cummulative normal distribution function (NORMINV in excel) based on a parameter in Tableau, and the new formula is quite long...
I don't get the error before I make the change but as soon as I do the viz breaks. Is this due to the size of my data set or number/complexity of my calculated fields?
You may be hitting a limitation of Jet here (the driver used to connect to flat files). It's ability to handle queries does stop at a certain level of complexity. Have you tried taking an extract after you made the formula change to see if it fixes the issue? I am suggesting this due to the fact that the Date Engine in Tableau can handle much more complex queries than the Jet driver.
Thanks Dan. I think you might be right, except that I am connecting to an extract, so it feels like it could be a limitation with how Tableau deals with extracts? For now I have restricted my parameter to a fixed number of values and hard coded the results instead.
If you are hitting the error both with a live connect to Excel and a Tableau Data Extract, the best thing for you to do would be to file a support case. It may be something that our team has seen before and can help with. You can file a case by filling out the information here: http://www.tableausoftware.com/support/request
Please do note that it may be requested that you provide a packaged workbook so that our support reps can take a look at the issue first hand. If it sensitive information and you cannot send that, it would be best to note that when you file the case
Thanks again Dan, I'll do that. I'm actually connecting to SQL Server 2012 but because I need to post copies of this workbook out to be consumed in reader I have to extract the data first.