I have Adobe Acrobat Pro Ver. 6. I also have Adobe Reader Ver 9. Each one works fine independently. But when I go to a website like irs.gov and try to download a form, Adobe Ver 6 pops up and I get an error message that I need to download Version 8 or 9 (WHICH I HAVE ALREADY DONE!!!!!)
When I have the option to download a form rather than read it on screen, there are no problems. But when the web page looks for Adone Reader it finds version 6 rather than 9.
I hate to take Version 6 off the computer because I use it to merge PDF files when necessary, but I guess I can if that is absolutely the only way around the problem.
You've found a common problem and one of the many reasons it's not recommended or supported to have these two applications on the same computer. The popular advice around here is to remove the one you don't want and leave the other. After removing one you may have to do a repair or reinstall of the other since it may get broken.
You may also try to direct your browser to open the correct add-on / application (Adobe Reader instead of Acrobat) when an online PDF is encountered.