RE: how to deploy the modified custom report in production GP, import and export will work for this report ??
I had to reply here because I was still having this issue event when all users were logged out of Dynamics GP.
Our setup: We have our REPORTS.DIC file inside of a shared folder that all of our GP Clients use that is located on the same server that our Dynamics SQL server resides on. This mapping reference is setup via the DYNAMICS.SET text file (ex. //server/gpshare/REPORTS.DIC).
The problem appears to be that when you open GP to import the modified reports, it opens the REPORTS.DIC shared file as a session (you can view this by launching "Computer Management" on the server that hosts the REPORTS.DIC file and then opening up System Tools > Shared Folders > Open Files), so even when everyone is logged out, I still had the error "Unable to open customizations dictionary", as it was technically open by myself.
What I had to do is, make a copy of the REPORTS.DIC file from the share and place it on the local computer, modify my GP client DYNAMICS.SET file to point to this local REPORTS.DIC file instead of the one on the GP shared folder, log into GP, import my modified reports, close GP, and then copy + paste (overwrite) the shared REPORTS.DIC file.
Running the GP client as administrator did not help this - it appears the issue is with hosting the file on a share (unsure why the file cannot be modified in GP while it resides in a share).
Hope this helps someone in the future!