For my situation, it wound up being that executing TimeSerial(0,0,secs) in some vbscript code, when the “secs” param value was greater than 24 hours.
Somehow out of all the different formats SSRS will export to, the Excel output was the only one running into this issue.
From the TimeSerial specs I don’t see anything inherently invalid about going that high… the docs indicate it simply rolls it into the day portion of the resulting value as I would expect. Given that the error refers to “Ole”, there must be some other intermediate data type conversion going on here… perhaps it passes through a time only type???