Create a new user account and see if the troubles follow that new account.
I've moved recently and, prior to moving, everything on my iMac (mid-2010) and hardwired HP 1300n printer were working relatively well. I was experiencing issues with the App store where it would say there were updates, tried to install them and, even though the App store said they were installed, they really weren't. They would always reappear as an update that hasn't been installed yet. I know this because I would check the version numbers. I solved that issue for the most part by manually downloading the updates from the Apple Support site and that worked - up till now.
Not only is that not working, but I now have a number of other issues since setting up my system in our new home.
1. I can no longer print anything to my printer. It's hard wired to the iMac so there are no wi-fi issues. When I try to print, I get a message in the print que window that "The printer is not responding" or "The printer may not exist or is unavailable at this time". I tried other cables and get the same results. In the Printers & Scanners preference, it says "In use" for my printer. I have only the one printer.
2. Up in the upper right on the Menu bar I use to have my name as the logged in user and was able to switch users there between my wife and I. That no longer exists.
3. The Date and Time indicator that usually appears in the Menu bar is gone. When I go to the Date and Time preferences. The Show Date & Time in the menu bar is unchecked, but when I check it, it disappears within a second continually.
4. I have the same issue as in #3 with the Time Machine icon in the Menu bar as well.
5. When I open Calendar, there is no scroll bar to move between the months when in month mode. It does appear when in Day and Week mode.
6. I'm on Yosemite v10.10.4. Trying to install Yosemite v10.10.5 over it no longer is possible either through the App store or manually.
I'm sure there are more issues I'm forgetting or have yet to discover, but I want to do something about this as something definitely seems corrupted. Here is what I have tried so far:
1. Ran Repair Disk Permissions through in Disk Utility.
2. Ran YASU, CC Cleaner, Mac Scan, and Onyx to no avail.
3. Tried re-installing the OS updates.
4. Out of the terabyte HD, I have 860 GB available, so lack of space is not an issue.
What I would like to try is a Clean Install but I have some questions.
1. The computer came with Snow Leopard. If I re-install that, will I be able to go straight to El Capitan with the free update when it is available or do I need to reinstall each update which followed Snow Leopard?
2. Should I stop updating the OS somewhere prior to El Capitan or even Yosemite because of my iMac's age (mid 2010)?
3. Besides my personal files/folders, is there anything else that you recommend be saved manually?
4. Is there any value in doing a Time Machine save knowing that I am having issues with what I have?
Although the computer is usable for the most part, I need to be able to print. I'm frustrated and need to do something about all these issues.
Your help is most appreciated!