While working on a ZERO project, all of sudden the Serial Monitor stopped working. The sketch would load properly with no problems at all, the Serial Monitor would also open with no trouble, but no Arduino message would be written. Sure enough Microsoft Security Essentials detected a bad Trojan in the system which clung to Google Crome.
If this problem is experienced, an in-depth sysem examination is necessary e.g. ("complete" for MS Security Essentials as opposed to "routine", which does not detect the danger) Of course all internal/external disks/dongles must be examined.
Is it offensive for the other participants to share technical info/experience of preminent general interest?
This info it has been posted here because, as stated, this problem has been experienced and detected with Arduino Zero. Furthermore the info will go on general research motors and will therefore be available to a much bigger audience. Just to have an idea, there are 655.000 issues on Serial Monitor not working on the net and, as far as I know, nobody seems to be aware of this specific difficulty.
There are many reasons the serial monitor might not show any information, including just bad coding on your part. Claiming everyone who has serial monitor issues is a symptom of virus is not appropriate.
I never wrote that viruses are the ONLY CAUSE of serial monitor malfunction. Viruses are just ONE new (at least for me) CAUSE. What I see in the replies is just a mis-interpretation of my post, because I described and mentioned ONE SYMPTOM, not the universal panacea against the problem described.
What I wrote is that while testing a sketch on Arduino Zero, the SM communications stopped. Since it took me some time to find the fault and to get rid of it, I am of the opinion that my post can help other guys who might find themselves at odds with the same problem while being unaware of what is going on.
If, on the contrary, the information given offended the sensitivities of other Forum participants, or is damaging to others in any way, or is hindering their work, I express my deepest apology and regret....
FURTHER INFO FOR VIRUS INFECTION BLOCKING SERIAL MONITOR
The purpose of this virus is to block your PC and/or data to make you pay a ransom. Even if you instantly switch the PC off and unplug the USB HD's/dongles, some files may be damaged. If you then rebuild the OS with stored system backup, parts of the virus in the USB HD's /dongles can still be alive and will block the Serial Monitor as described, without any further action. The best procedure is to clean with antivirus (Microsoft Security is excellent) all storage media.