Where is the log file?

The log file is usually in the same folder where your installed the software.

I tried but sadly did not find it.

Log file is generated when you have some error only.
You must also have permissions to write into the same folder.

Today I installed the new version and sniped an item. It did not bid. I have used myibay for a long time and there has not been a failure for a long time. Works fine every time. I have writing access everywhere on my system and system files are not hidden. I wonder what happened.

Log files are generated when there is an issue with the software itself, not with your snipes.
You can check the status of your snipes by opening "Snipe" windows and checking out "My Status" field on the bottom.

P.S.: there was a network issue today for some short period of time so a few snipes failed. I'm very sorry if you were affected by that. It's back to normal since than.

Thanks, Sashka! Your help is great. Will be sniping again tonight so we'll see. Have changed the time from 7 seconds to 12 seconds to be sure.

Is there any commandline flag I can raise in order to force full verbose logging?

There is logging on a client side. The only way to see your results is checking out your "My Status" field or putting your e-mail address in Profile so you will get it by e-mail.

I have my email adress in the Profile and it normally sends me emails about the outcome. Not so last time.

If you activated your snipe too late, it will not snipe and will not send an e-mail too:
http://www.myibay.com/login/faq/4/#q5

If you don't see "My Status" field, then you let me know the item number so I could look up and tell you what happened.

This time it worked perfectly again. Spot on the second I entered in the profile. So must have been like you said. Thanks!