Adobe Reader may be being blocked by:
1. Your Internet Settings
How to use Reset Internet Explorer Settings (RIES
To use RIES in
Internet Explorer 7, follow these steps:
1. Click the Tools menu, and then click Internet Options.
2. On the Advanced tab, click Reset.
3. In the Reset Internet Explorer Settings dialog box, click Reset.
4. When Internet Explorer 7 finishes restoring the default settings, click Close, and then click OK two times.
5. Close Internet Explorer 7. The changes take effect the next time that you open Internet Explorer 7.
Note for users who cannot start Internet Explorer 7 for some reason, use RIES from Internet Options in Control Panel.
Refer here:
http://www.microsoft.com/windows/ie/community/columns/ietopten.mspx
For even more options
2. Your Firewall
This may include Windows firewall
If you are using a 3rd party firewall, please open your firewall and locate where to default the firewall settings
It may also be required that you will need to fully un-install your firewall (as in some cases the default settings, do not default all settings
3. Live protecting programs
Such as Spybots Search & Destroy, or any other program
starting with your computer, and that has been set to disable Adobe from running
The easiest option here, is to again remove (un-install) the live protecting programs
4. Adobe program issues
Please un-install then re-install
Adobe Reader (also complete all Adobe updates on top of this)
5. A Windows settings issues
There are actually many settings in Windows that can cause this
Including:
Default startup application for Adobe being corrupted
Group Policy settings being set to disable Adobe
Even your Hosts file being set to disable certain links
Or possibly even Windows itself requiring to be repaired
These areas can be very critical, and hopefully you will not get to this point!
6. Virus\Malware issue
Virus or Malware can cause lots of different issues and strange behaviour on users computers. If you feel you have tried everything, then have a look at:
Viruses/Spyware/Malware Preliminary Removal Instructions
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If the above still does not help, approach Adobe directly!