It seems that you are not allowed to modify the file mentioned.
Go to the directory mentioned in the error and see its permissions from properties. If you do not have the permissions on this folder hierarchy, get yourself added there.
Also, if there's some file backup software running on your machine, disable it and reapply the update.
I've gotten this error on 3 laptops.
They are all Windows 7 pro 64bit SP1 Dell fresh installs.
I then download the trial of Adobe Acrobat X Pro and install it just fine.
I then go to update and get a Error 1321. If I retry the update, I get the same error but on a different file.
I'm pretty sure at this point that the installer is messed up somehow, maybe just for 64bit machines or something.
I'm going to try a variety of troubleshooting steps. I'll post back if I find out anything.
Ok, I just solved mine. I can't state exactly which part of the below steps 'fixed' it but I recommend.
1.) Uninstall all adobe software (for me that was flash, reader and ofcourse Acrobat Pro).
3.) Right click the Adobe Acrobat Pro installer and 'run as administrator'
4.) Install ran fine and then the update worked too.
Let us know if that works!!!!
Typically for installations, you have to be logged in as the administrator (at one point it had to be that exact name!) and have anti-virus disabled. You have succeeded and that is good. This is just to make you aware for the future.
This worked for me.
1) Uninstall adobe acrobat pro x
3.) Rename c:\program files\adobe\acrobat 10.0 c:\program files\adobe\oldactobat 10.0
4.) reinstall adobe acrobat pro x and update.