It's more likely that it was the "plugin" for the browser caused the problem.

Sometimes the creators of the browsers release updates that the plugin creators don't have access to and so cannot test.

It could also be related to the actions of the browser when a PDF is detected. Ie does it launch the stand alone Acrobat Reader (as per Safari) of does it open in the browser window (as per Firefox).

If you're on a Mac, another option may be to use "Preview" as it will recognise PDF files too.