Good idea, checked the first tray icon it is related to the software program tuneup utilities.
I am checking tuneup utilities configuration to see if it blocked the printer when external hard drive turned on. Maybe some security setting, still looking.
Tune up programs that monitor your system will be running in the background and the possible driver conflict/failure which now seems to have been the cause of the printing problem may well have caused it to pop up.
I've seen my Norton icon pop up similarly when I've been running something or other.
It's still popping up when external hard drive turned on and printer is printing O.K., it doesn't pop-up when printing with the external hard drive turned off.
Continuing to investigate tuneup utilities configuration with external hard drive.....
It's possible that as it's monitoring your system files, when the HD is switched on - it is detecting that change, but if everything is working fine then I wouldn't bother yourself with it.
It's possible that one of those driver updates resolved a compatibility issue with the HD and the printer's drivers and has nothing to do with Tuneup Utilities.
that's what I'm thinking, too
I made some configuration changes to tuneup utilities and the icon no longer pops-up.
continue to monitor the external hard drive and wireless printer, if the printer error message occurs again, I'll post back what I've found.
Thanks again for your continued effort! Excellent info in the posts and good reference for others.
You're welcome and glad that you found the cause of the printing problem.