I would like to add some info about my configuration: Win XP SP3, Chrome 8.0.522.224 (with Chrome PDF Viewer disabled and Adobe Reader 9 enabled), Avast 5.0.667, virus defs updated to 31.12.2010.
This is quite likely to be a factor in this issue, the latest virus defs are 110105-0 (5th Jan 2011)
Your virus database is 5 days out of date. Try updating the defs and rescanning the pdf file.