Got a document with this same problem (Acrobat X): "The font 'OPSUFont0' contains bad /widths."
Printing and rescanning the offending page has been the past solution.
Took a closer look using Preflight > Analyze > Overview > Fonts --- the difference from other fonts in the document is "Font defines differences from base encoding"
When that is clicked upon, it goes to the page and there is a little place delineated with blue lines.
Problem isolated -- How to fix it?