Cannot Save/Edit to Mac Share Using Mountain Lion The problem: Under Mountain Lion (10.8.3) I cannot create new files or save changes to a particular share, which is running Lion (10.7). 

I can connect to the shared Mac on my local network (in a business location). I am the administrator of both machines. The remote computer I'm connecting to has several shared drives, and these problems affect all of them.

What I cannot do on the shared drive


Create a new file
Save (re-save) an existing file I've opened


What I can do on the shared drive


Create a new folder
Delete folders and files
Rename folders and files
Move folders and files


Additionally, the following quirks apply:


I can view the full file system on the remote computer, including system files; in other words, I am successfully connecting as an administrator user
If I try to drag and drop a file from my computer to the remote computer, I get a dialog that says "Finder wants to make changes. Type your password to allow this." This is strange, nonstandard behavior for an already-autheticated admin user doing a simple copy operation to the remote machine. 
If I type my password and continue, I get another dialog that says "A newer item named [file name] already exists in this location. Do you want to replace it with the older one you're moving?" This is a bogus error, because a newer version of the file did not exist on the remote server. If I click "Keep Both", Finder seems to hang, but it actually begins to create tens of thousands of zero byte files on the remote server: file name-1.png, file name-2.png, etc., all the way up to file name-30000 or so if I don't stop it. However, if I click "Stop" instead of "Keep Both", it cancels. If I click "Replace" it creates a zero-byte file with the correct name, and then gives an error that says "The operation can't be completed because an item with the name "" already exists."
Console reports an error when I try to copy to the remote machine: Application App:"Finder" [ 0x0/0x25025]  @ 0x0x7fc4ea63e640 tried to be brought forward, but isn't in fPermittedFrontASNs ( ( ASN:0x0-0x4d04d:) ), so denying. I've also seen this error, but it doesn't happen every time: WindowServer[120]: [cps/setfront] Failed setting the front application to Finder, psn 0x0-0x25025, securitySessionID=0x186a5, err=-13066.


I have tried the above using a computer running Lion, and had no problems. This issue only affects my new iMac running Mountain Lion. In this case, Mountain Lion was factory installed. However, I imported my user settings from my old Mac Pro during the install process. 

This problem is very similar to one reported by another user at Network share permissions problems in Mountain Lion, but there are some differences, so I asked a separate question. Among other things, there are no applications on my system that "ignore the problem" as in that user's case. 

What I've tried/verified:


I routinely repair permissions on my iMac, so I'm sure that is not the issue.
I have verified that the files/folders have the correct sharing permissions.
Other uses, including a Mountain Lion user on another machine, can copy/save files to the remote computer.
Deleting the Finder preferences file (~/Library/Preferences/com.apple.finder.plist) did not help.
Logging is as the Guest user on my local machine, I could connect and copy files to the remote computer. This suggests the issue is limited to my local user account. 
If I use Terminal to do the copy, I get an "Operation not permitted" error. It creates a zero KB file on the destination server, as before. However, I discovered by accident that if I immediately do the same command line copy operation again, without deleting the zero KB file, it successfully copies. I guess for now this will be my workaround.
After spending maybe 12 hours or more troubleshooting this issue over the past month or so, and realizing it was isolated to my user account, I decided to recreate my user account from scratch. This has solved the problem, and I am now able to connect to the remove server and add/edit files without difficulty.