Update: For some reason, Adobe Acrobat stopped working as well (same error as Reader).
We do have have a seperate "Test" sharepoint foundation 2010 environment in seperate test domain which isn't using SSL and I have exhibit no issues open PDF files in Adobe PDF products.
The only difference between the two environments is that we have SSL only enabled in Production with a non-standard port. I am going to test this in the test SP with a standard ssl 443 port to see if it still works.
Is there an issue with Adobe products understanding non-standard ports?