HP Laserjet printing strange icons

I'm posting at Apple because in trying to fix the problem with the printer I ran into conflicts between OS X and the HP utilities.

Initial Problem

The HP Laserjet Pro M102w attached to my iMac has started printing icons down the right hand side of the page.

The only recent change I can identify is that I had to change the cartridge but I used genuine a HP component so I'm assuming there were no problems there.

Initially I turned the printer off, disconnected from power and left the printer disconnected for 10 minutes but when it was reconnected the problem was still there.

My research into causes only surfaced the possibility that there might be a problem with the driver. 

Problems with Reinstalling the Printer Driver

I understand that to update the driver I need to use the Easy Admin HP utility. However, my Mac refuses to install the utility with a disturbing message saying that the program will damage the computer. There is no other explanation and no suggestions as to what else to do.

At this point I've stalled, not sure what other approaches I could use in trouble shooting or trying to replace the driver.

I'd appreciate any suggestions as to the the cause of the problem with the icons appearing down the right hand side of the page OR how to deal with the driver update utility problem.

Thanks