have you tried putting a breakpoint on the code before the report fires, that way you can call the values in the debug window. so long as the information has been passed you could put the breakpoint anywhere

then you can find what the exact value are (or even if they are being found) in the immediate window
ie:
?([Forms]![ReportSelection]![BeginningDate])
?BeginningDate()


and if one of those work, you can then test the formatting