Decode Stack Trace Not Working

I'm evaluating SamrtAssembly 5.1 (build 3) and so far I'm very impressed. But I am having difficulty getting the Decode Stack Trace option to work. I've created a .pdb file (which I've also chosen to obfuscate) so my stack trace has it's line numbers and looks something like this

at AnalysisClass.Base.‡() in #Ixf:line 761
at †.Œ.‹‰(Object IndexObj) in #5zf:line 4225
at †.Œ.†