Getting "#Error" in SSRS reports - how to diagnose?

I have some custom code that gets called to format certain fields for an SSRS report. Instead of getting the formatted value back as expected, I get the unhelpful message of "#Error". Is there a log or anything that 开发者_开发百科can give me some useful information?

I have verified that the assembly is in the "C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\PrivateAssemblies" folder. I copied it over as soon as I built it. I was told not to reference this one from the actual report itself, so I reference the assembly where it was originally built. Someone else in my company does the same thing and her machine is not throwing these errors.

I have also tried both release and debug versions of the assembly, but that does not make a difference. Googling is worthless too, because it keeps matching "#Error" to "Error".