A little (and I hope interesting) update:
Yesterday, I posted on Yahoo's own user forum, where people like me query others on issues that they're experiencing with their accounts. Yahoo staff also read the questions, and occasionally provide information.
My question - deliberately provocative - was similar to the one posted here: was it possible to hack into one's own yahoo mail account. There were no answers forthcoming since yesterday, and then suddenly, a computer-generated message from yahoo itself suggesting that I check the thread I started. When I did, I noticed that nothing had changed: still no answers.
A while later, I tried to log into my alternative yahoo.fr account and got the same error messages as on my (hacked?) primary yahoo.com account: I was locked out for a second time!
This time, I was ready for them, however: I had carefully entered all the correct information for the security questions necessary for generating new access. And this time, once again, the answers were rejected as being erroroneous!
Eureka! I think I'm starting to get it: I think that it's Yahoo itself that froze my accounts both times. The first, probably after being notified by PayPal that the account had been used to breach their security for a fraudulous transaction. The second, after posting a query about hacking Yahoo's mail system on their own forum.
The first account might have been retreivable if I had had the proper answers to the security questions.
The second was probably just cancelled by Yahoo - despite my having the necessary answers - for having sollicitated hacking info on my account and right in their face, so to speak.
Makes sense, no?
I was able to open still another new yahoo mail account afterwards, which would mean that they haven't blocked my IP address.
I'm curious to see how long this one will last - and if I've actually figured out what's really behind this mess.
It would explain the lack of enthusiasm and robotic responses of the customer service reps when I called: if the first account had been frozen for security reasons, they would have been doubly attentive to attempts to re-open it.
Hmm...
Am I over-analysing here?