Thanks to the links provided by dhouwn
(much appreciated!) I've been able to more precisely pinpoint when my problems started.
The Flash logo issue with ppradio.dk was introduced with 2.3.3 RC3 and I'm reasonably certain it's due to this bug fix (which apparently has introduced a new bug):
+ [ClearClick] Protection against partial obscuration via Flash objects with OS-native wmode values (thanks David Lin-Shung Huang for reporting)
The crash problem seems to have been introduced with 2.3.6 RC4, since I do not experience any crashes using 2.3.6 RC3.
EDIT: I've now also been able to pinpoint since when the "Forbid Adobe Flash" option on the Embeddings tab had to be unchecked in order to view the Flash logo on ppradio.dk. That was introduced with 2.0.9 RC4. Prior to this version a 100% whitelisting of the site would also show the Flash logo.
I still can't reproduce the ppradio.dk issue on either Fx 2 or Fx 3 (athough in F2, I had to whitelist the site in AdBlock Original, which wasn't supported in F3+).
But since we're at an impasse, and you've identified certain version changes correlated to each issue, I'll escalate this to Giorgio. Thanks for your results.
Also, the link to the version history does *nothing* right. I thought it was supposed to provide links to actual old versions, but even if it's intended to provide a link to the latest stable version, that's wrong, too, as the current stable release is 2.3.7. AMO apparently doesn't have this yet, if you search through their site. I'll let Giorgio know that, too. @ dhouwn:
I've bookmarked your feed link for the actual .xpi's, and will add a shortcut to it. Thanks for this most welcome contribution. (inside joke.
What you said about Java supports what I said: It's a plug-in, not an add-on. You're welcome for that knowledge. (same inside joke.
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:18.104.22.168) Gecko/20120306 Firefox/3.6.28