the acrobat reader that is running cannot be used to view PDF files in a browser

This worked for me:

Start

Run

regedit

Browse to HKEY_CLASSES_ROOT\Software

Right click on Software, New, Key

Type Adobe and hit enter

Right click on Adobe, New, Key

Type Acrobat and hit enter

Right click on Acrobat, New, Key

Type Exe and hit enter

Click on Exe and double click on (Default) on the right and enter the text below including the quotations:

"C:\Program Files\Adobe\Reader 9.0\Reader\AcroRd32.exe"

Click OK

Problem solved.

Good luck!

Same problem here, but different solution.  This is for MS Vista operating system.  Start Adobe Reader 9, then choose Edit, then select Preferences.  Then click Interent under the Categories Menu.  In the Web Browser Options section, you will see 3 boxes.  Check only the Allow Fast Web View box.  Click OK,  then exit Acrobat Reader.  Restart Internet Explorer.  Hope this helps!

Thanks for the information. 

I have install Adobe Acrobat Reader 9.3 and view online ebooks and it works well. maybe the website you login doesn't support. Can you show me the website and the details about the error? As far as I know, adobe reader can dierctly view .pdf webpages.

I installed Adobe Acrobat Reader 9.3 last night and was having the exact same problem.  This morning I went to "START" and in the "Start Search" box/option I typed "Adobe" to see if I could find any older versions that might be competing with the new 9.3.  As soon as I started the search (clicked on the magnifying glass) I received the message that the computer needed to initialize Adobe Acrobat 9.  As soon as it finished initializing I could open any PDF in a window browser.

I have found the same issues with some of the PC's on our network. So I will give an example: We are a group of Auto Dealerships, and one of my users was claiming that on a website that they use for work purposes (a General Motors Website) that a particular location that he goes to within the website he clicks on a link to download a PDF file. So he will click on the link, and the PDF file opens up. Then he will close the PDF file, and click on the same link and the web browser will lock up for about 90 seconds. Eventually you will recieve the mysterious message ( A problem has been encountered with Adobe Reader and must close) So you allow Adobe Reader to close and if you go to any other website and open Adobe PDF files within IE 7 all open fine, no problem at all. So I 1st went after IE7 thinking that there was an issue, so I downgraded back to IE6, and still the same issue. So then I upgraded to IE8 and still the same issue. Booted the PC in Safe Mode, and the issue goes away, so now I am wondering what does not load in IE when in Safe Mode. I then in turn upgraded to Adobe Reader 9.3.1, and still the same issue, but not when in Safe Mode. So what fails to load in Safe Mode when opening IE. The Google Toolbar. So I uninstalled the Google Toolbar, and no issue from that point on. So I went and downloaded the Google Toolbar again, and low a behold, the issue crops right back up again. So does anyone have any ideas as to why the Google Toolbar would be causing this issue?

I have spent hours on this crap - really annoyed me.  We pushed this out via GP with the Customisation Wizard stating is Acrobat installed use this first etc...

We got the following error:

'The Adobe Acrobat/Reader that is running can not be used to view PDF files in a Web Browser. Adobe Acrobat/Reader version 8 or 9 is required. Please exit and try again.'

However after following all the advice, none of it worked.  I could not get the cannot be used message to go away.

However...

I have fixed my issues.

Run this regedit script or enter it manually.  Do not forget the quotes in the file location bit - that matters!

--------------------------------------------------------------------------------

Windows Registry Editor Version 5.00

HKEY_CLASSES_ROOT\Software\Adobe\Acrobat\Exe]

@="\"C:\\Program Files\\Adobe\\Reader 9.0\\Reader\\AcroRd32.exe\""

--------------------------------------------------------------------------------

This has worked every time, make sure you run it as an Administrator.  I hope I save you guys some time!

Steve

1. Check here

2. Then review browser options...select correct reader.

I was able to fix this by opening Adobe Reader 9 and going to Help > Repair Adobe Reader Installation.  I was surprised this simple trick did it after months of investigation and trial and error.

I'm running Firefox.  I also have both reader and Acrobat installed.  I had to go to Tools/Options/Applications scroll to Adobe Acrobat Document and set the dropdown to "Use Adobe Reader 9.1 (default)".  It had previously been set to "Always Ask".  That seemed to work.  I also did the same thing in IE (the menus are a bit different), and I could open them in IE, too.  I'd previously made sure all the old files from previous versions were deleted, as suggested by others.  I also set both Reader and Acrobat to not open in browser as suggested by others.  Not particularly intuitive set of steps, but it seems to be working now!