I had this weird error the other day, when all my report definition .rdl files seemed to get corrupted somehow. I’m not sure what caused it but it might have been something to do with Tortoise SVN.
The error was something like “[rsInvalidReportDefinition] SSRS the report definition is not valid. Details: ‘.’, hexadecimal value 0x00 is an invalid character”. A screenshot is below:
When I opened the rdl it looked fine, and when I viewed the source of it in Visual Studio it also looked fine. But the telltale sign was that I could not delete the last character in the .rdl file, a ‘>’ which closed off the final </Report> tag. In the end the fix was quite simple, all I did was delete that last </Report> tag and type it in again.