Problem getting geoprocessing tool with multiple input variables web enabled

[MikeHouts]

I have a geoprocessing tool that works fine in my desktop, but wont run once web enabled. Simply put, the model requests two inputs from the user. 1) an input file from the user, and 2) a user defined buffer distance.  The model  then proceeds with many more steps and produces an output file. The input file variable works fine, but I cant get it to run with the buffer distance set as a variable (either unrestricted or via a predetermined list).  I have had success web enabling other geoprocessing tools with just an input file variable, the only difference is that this sets the buffer distance as a parameter.

Working in ArcGIS Server v10.2.1,

Any help how to get the model to run would be greatly appreciated.
Thanks, Mike

[WilliamCraft]

By "web enabled" are you talking about publishing your tool as a geoprocessing service?  What error are you getting on the screen or in the ArcGIS for Server log file?  Is the buffer distance a mandatory field?  Try inputting no value at all or inputting 0 instead or some other number... is the output still properly produced?