Hi gordon56y, did you disable the Adobe plugin on the plugins list here:

orange Firefox button (or Tools menu) > Add-ons > Plugins category

When Firefox encounters a PDF, it should use your preference on the following tab for what to do with it:

orange Firefox button (or Tools menu) > Options > Applications

After allowing a few seconds for Firefox to display the list, you can type or paste pdf in the search box above the list to filter it.

If the previously selected option does not exist because you disabled it, I think it might either use the built-in viewer or open the file in the system default application.

jscher2000,

 Yes I had disabled acrobat reader using:

Tools > Add-ons > Plugins

When I go to: Tools > Options > Applications I have pdf set to acrobat reader

When I open a pdf in FF, it is using acrobat reader, not the FF built in viewer (they look much different). The viewing of a FF pdf looks the same, whether reader is enabled or disabled.

My current setup probably an acceptable workaround.

Adobe does not yet have an acrobat reader 11.0 for vista  :-(

When I open a pdf in FF, I get reader 10.1.7 (latest 10.X version)  :-)

And I do not get that false FF acrobat reader error  :-)

And I will have to wait for Adobe to update acrobat reader to 11.0 for vista. (sigh)

thank