Having trouble with Red minus signs on folders shared to my computer

Question

Here's the situation as best as I can describe it.
We are working on 2 imacs.  iMac A as a 1TB harddrive attached to it via USB that has all the folders on it that we use to work.  iMac B is connected to A wirelessly and can "usually" access the contents of the harddrive through A with no problems.  However, every once in a while I click a folder on the harddrive and I get access (I'm on iMac B) to that folder but the subfolder inside that I need to access (the others are fine) has a red minus sign on it which is infuriating.  So far the only way we've been able to re-grant access to the folder for me is to either restart my computer or unplug and replug the harddrive into iMac A.
Steps we have taken:
Added full "read & write" permissions to both computers and users on both the folder, the sub folder, and the harddrive itself
Attempted to set up additional users to access the folder differently
Checked and unchecked "ignore ownership" on all of the above access points
We find it strange that it's only sometimes I get locked out of the folder and other times I'm not.  It has to be some sort of glitch unless there's some sort of setting that locks me out if I make too many changes to the contents in that specific folder.  Any ideas or help would be greatly appreciated.

Answer 1

The procedure below will reset the permissions of a home folder in OS X 10.7.4 or later. If you're running an earlier version of 10.7, update to the latest version first. This procedure should not be used in OS X versions older than 10.7.4.
Back up all data before you begin.
Step 1
Click the Finder icon in the Dock. A Finder window will open.
Step 2
Press the following key combinations, in the order given:
Command-3
Shift-command-H
Command-I
The Info window of your home folder will open.
Step 3
Click the lock icon in the lower right corner and authenticate with the name and login password of an administrator on the system. If you have only one user account, you are the administrator.
Step 4
In the Sharing & Permissions section of the window, verify that you have "Read & Write" privileges. If not, use the "+" and "-" buttons in the lower left corner to make the necessary changes.
Step 5
By default, the groups "staff" and "everyone" have "Read Only" privileges. With those settings, the files at the top level of your home folder will be readable by other local users. You can change the privileges to "No Access" if you wish, but then your Public and Drop Box folders will be inaccessible to others, and Personal Web Sharing won't work. Most likely, you don't need to change these settings.
Step 6
If there are entries in the Sharing & Permissions list for users or groups besides "me," "staff," and "everyone," delete them.
Step 7
Click the gear icon at the bottom of the Info window and select Apply to enclosed items... from the drop-down menu. Confirm. The operation may take several minutes to complete. When it does, close the Info window.