Easier said than done. Adobe Drive CS4 x64 is installed as a dependency of Photoshop CS4 x64. It cannot be uninstalled without removing Photoshop; at least, not using the Adobe installer anyway.
Originally Posted by fiskie
Not to be deterred, I uninstalled Adobe Drive manually. First I unregistered the DLLs by running (as administrator)
Then I ripped all references to "Adobe Drive" out of the registry using regedit, and finally I deleted the C:\Program Files\Common Files\Adobe\Adobe Drive CS4 folder.
regsvr32 /u "%CommonProgramFiles%\Adobe\Adobe Drive CS4\ADFSMenu.dll
regsvr32 /u "%CommonProgramFiles%\Adobe\Adobe Drive CS4\AdobeDriveCS4_NP.dll
And now EAC works again, and Photoshop seems to get by just fine without Adobe Drive! Thanks for your advice fiskie!