I have not worked with mod_pagespeed yet, so I can't say for sure. My guess is that something is getting corrupted in the file when it is sent over, but I can't tell for sure without seeing it. My recommendation: try using the non-minified version and see if it gives you a line for the error. If that doesn't work, send me a link to a dev server with it using mod_pagespeed and I'll see if I can help suss out the issue.