[TonyLima]

It might depend on your IP address -- if you are unlucky enough to come from one of a block of addresses that Yvonne saw spammers or DOS attackers coming from. I am not very familiar with configuring that in the board software but will try to take a look.

The above was only a guess. 

Unfortunately I am unable to figure out what is going on. I spent half an hour looking through all the MyBB admin settings that looked likely, plus googling. There are a few different anti-spam plugins installed, and maybe some stuff in the base software, but I don't know what is requiring some long-term, innocent users to solve a captcha from time to time or what settings might be changed to affect that. It never happens to me, FWIW. So far I've seen several people report it in this thread. BC and Marty also mentioned in the Moderators private forum that it happens to them -- so being a mod evidently doesn't help.

Yvonne and George know way more about MyBB setup and configuration than I do. I learned a little more when helping George do the transition to the new site, but I still don't know a lot of things.

Thank you. I really appreciate the time and energy you folks put in. FWIW the problem seems to have gone away.

[TonyLima]

It might depend on your IP address -- if you are unlucky enough to come from one of a block of addresses that Yvonne saw spammers or DOS attackers coming from. I am not very familiar with configuring that in the board software but will try to take a look.

The above was only a guess. 

Unfortunately I am unable to figure out what is going on. I spent half an hour looking through all the MyBB admin settings that looked likely, plus googling. There are a few different anti-spam plugins installed, and maybe some stuff in the base software, but I don't know what is requiring some long-term, innocent users to solve a captcha from time to time or what settings might be changed to affect that. It never happens to me, FWIW. So far I've seen several people report it in this thread. BC and Marty also mentioned in the Moderators private forum that it happens to them -- so being a mod evidently doesn't help.

Yvonne and George know way more about MyBB setup and configuration than I do. I learned a little more when helping George do the transition to the new site, but I still don't know a lot of things.

Thank you. I really appreciate the time and energy you folks put in. FWIW the problem seems to have gone away.