SAGE ACT - Save File Error - Saving Existing ACT 2009 Attachments results in - File is currently in use. Please Try Again Later.

Can you check that the users a FULL control to the Supplemental Files folder ... you might try adding the users explicitly rather than just "Everyone".

Saving a file also means deleting the temp file that editing creates, so this might be the issue

I've checked and Domain Users and Everyone have Full Control in Both NTFS and SMB permissions through all folders of the directory tree.

Also, I checked effective permissions for the folders and they are coming up right for the domain users as themselves and as a group.

Can a user open and edit a file in the Attachments folder without ACT!?

Same problem as when opening through ACT

By the way, I've migrated ACT to a new server.  The problem existed on the old server, as well as now existing on the new server.Went from 2008 to 2008R2.  And again, it's not a permissions issue, it's not access is denied, it's file is busy.

As an added piece of information. All users have no problem creating a new file in said directory, only updating existing files.

Well, if same problem without ACT!, not an ACT! issue ... try some of these:
http://support.microsoft.com/kb/129276
http://support.microsoft.com/kb/313937
http://support.microsoft.com/kb/271513

Does it work if you log in as a Domain Admin?
Does it work with a txt file rather than Office?

Text files are fine.  Domain admin makes no difference.  My account is a member of Domain Admins, and I get the same error.  

Those articles refer to a document open by multiple users, which this is not.  I'm wondering if ACT! uses some sort of indexer and that is locking the file permissions.

ACT! 2012 indexes the attachments ... none of the previous versions do. ACT! 2009 wouldn't touch the files other than when called

Most of those articles refer to issues other than the file is open by another user. You should take another look

another thought ... you might try disabling any antivirus and windows search index on the server temporarily to see if they might be causing it

Failing all that, use the MS Process Explorer and see if it shows if something is locking the files:
http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx

We have seen this several times.  Here is what worked for us.  Do a backup of the database, open actdiag and detach the database.

Then move the original database, (ALF, ADF, supplemental files folder) to a folder called OLD or something, but clean out the original file location.

Then Open ACT, do file, RESTORE AS, and restore the database under the exact name to the original location.

Don't do this if you aren't sure. Also if you have sync databases, it will break them, so don't use in a sync environment.

However if you are just terminal server or Citrix, it should fix it.

I will look into your solution.  We have remote sync turned on right now, but soon that will no longer be required as we are deploying VPN to our remote users.  I'll post back once we can turn off Network Sync.

I usually find VPN a bit to slow for most users...
http://blog.glcomputing.com.au/2009/11/supporting-remote-users-with-act-by.html

I understand that concern, however, security concerns override the performance issue.  We have 7 remote databases.  They are limited to their contacts plus vendors and some shared customers.  It's a bit of a risk when they can export to a csv quite quickly.

Then I get into remote printing issues.  It's all a series of compromises.  ;)

Remote printing isn't that hard ... just need to drivers for each remote printer installed

Thanks!