MutSig Preprocess error

I am trying to run MutSigCV on the GenePattern site. I do not have a "categ" column for my data, so I need to use the preprocess step; however, I am getting an error indicating that there may be a build mismatch between my mutation table and the chr file ("Error using gp_MutSigCV>MutSig_preprocess (line 553) possible build mismatch between mutation_file and chr_files"). I generated the file by using Oncotator and the build is hg19, which is the same build I am using in MutSig, so I am not sure why I keep getting this error. I'm using the shared coverage table and mutation type dictionary files. Wondering if anyone here has had any experience with this and could offer some advice?