Have you changed any settings of Windows or installed/removed any softwares since you installed extensions successfully last time? What error message are you getting when you install extension? Have you tried to run Extension Manager by right clicking icon and selecting "Run as Administrator"?
What level of UAC on a Win 7 Enterprise is needed to enable/disable InDesign CS5 plugins with the Extension Manager? On a Win 7 machine with UAC enabled, I can successfully install the .zxp file and run the Extension Manager to install my plugins. However, when I run EM to disable them, I get an 'you do not have permission' error. This happens for an administrator user and when right clicking EM icon and selecting "Run as Administrator".
I can enable/disable them only by disabling UAC completely and rebooting.
I am only trying to enable/disable our one extension, which contains 3 .pln files and their associated Resource folders. This is a problem that started when the plugin changed from Enable_for_all_disable_for_one to Enable_for_all_disable_for_all. (see [http://forums.adobe.com/message/4053573#4053573]) I can provide the .zxp file if you will tell me how to upload it. I could also provide a log file, if I knew where it was and/or how to enable it.
I have sent a private message to you. To enable log files, you have to create a file named "ExManLog.YES" in the same folder as Extension Manager executable file. On Windows, it is install folder; on Mac, it is "/Applications/Adobe Extension Manager CS5/Adobe Extension Manager CS5.app/Contents/MacOS". You will find the log files in "C:\Users\<UserName>\AppData\Roaming\Adobe\Extension Manager CS5" (Windows) or "/Users/<UserName>/Library/Application Support/Adobe/Extension Manager CS5" (Mac).
You can mark this issue answered.
My Plug-Ins were installed as 'Enable_for_all_Disable_for_all' to "Program Files (x86)\Adobe\Adobe InDesign CS5\Plug-Ins\My Folder". Since they are in the Program Files (x86) folder, they get special permissions. When the Extension Manager CS5 is launched from the InDesign CS5 Help menu "Manage Extensions...", and UAC is enabled to the Default level, it does not have sufficient privileges to manage the extensions. When EM is run from the Start menu with 'Run as administrator' it is able to enable/disable/remove the extensions as expected.