Scope has latest firmware (2.41) and has been problem free.
Turned it on today after a month of sitting unused and attached a N2863B probe that originally came with it to input 1.
Screen displayed error message essentially saying "invalid probe connected, remove invalid probe and press OK".
Connecting the 3 other probes I got with this scope gave the same message.
Also, connecting any of the probes to each of the 4 inputs gave the same message.
Probes are known good (verified on other machines).
3 scope power-down restarts didn't clear the problem.