MutSig Preprocess error

Hi,
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?
Thanks!