OS X does not remember my network passwords anymore
This might be a permissions issue.

I sometimes have similar problems with settings not getting saved when the home folder has bad permissions (probably issues with the ~/Library folder). Using the terminal command resetpassword from the recovery permission may help as per http://osxdaily.com/2011/11/15/repair-user-permissions-in-mac-os-x-lion/


Restart using the recovery partition (hold down Command+r when restarting)
Under the "Utilities" menu select "Terminal"
In the Terminal window, type resetpassword and hit Return
When the Password Reset Utility launches, select the startup drive's icon and then select the user account that is having the difficulties (or go through one-by-one and select them all)
Click on the "Reset Home Directory Permissions and ACLs" button at the bottom.


Unfortunately, recent versions of macOS (10.14 and above maybe?) do not seem to have this feature within the Password Reset Utility. This seems to do the same thing without the Password Reset Utility or requiring restarting in the Recovery Partition. From https://support.apple.com/en-us/HT203538


From the Finder menu bar, choose Go > Home. Your home folder opens.
Choose File > Get Info. An Info window for your home folder opens.
If the Sharing &amp; Permissions section at the bottom of the window isn't open, click the triangle in that section to open it.
If the lock at the bottom of the window is closed lock, click the lock and enter an administrator name and password.
Click the action menu , then choose “Apply to enclosed items.” Click OK to confirm the action.
A progress bar appears at the top of the window. When done, restart your Mac.