Adobe Reader 9 issues in Opening PDF File

Hello!
The new Adobe Reader 9 version gives me a pop-up window shown below when opening PDF file.
I am not able to guess whether it is a problem with new PDF Professional 5 I am using or with the Acrobat Reader Plugin(Firefox 3 and Flock v.1.2.3).
There should be a problem with the browser because PDF doesn’t open in Opera & IE7 too without the error message.

iTunes + QuickTime
The installer has encountered an unexpected error installing this package. This may indicate the problem with this package. The error code is 2324.
OK
The Adobe Acrobat/Reader that is running can not be used to view PDF files in a Web Browser.
Please exit Adobe Acrobat/Reader and exit your Web Browser and try again.
