Binary package hint: lyx
Lyx developers use assertions everywhere, and in particular for certain sanity checks on the graphical aspect of insets. The result is that if you turn on assertions you get continuous crashes that certainly don't make you happy when you need to work with lyx. On the other hand, the only assertions I ever saw triggered (and I use lyx many hours per day) are related, no need to say it, to the aspect of insets when crossed by the cursor, when navigating a document using arrows. In particular, editing an array becomes impossible if you don't use the mouse, while it is natural to use the arrow keys to move up and down in an array.
For all these reasons, I ask you to please disable assertion checking by using the --disable-assertions flag to configure. I did this and built my own package, however lyx will not be usable in ubuntu without that flag. Other distributions (at least fedora) do this as well.
Assertions are disabled by default in configure in lyx, this clearly meaning that they are not meant for production use, however debian developers enabled those, to help debugging. This is ok since lyx 1.4.3 in debian is in unstable, but it is not ok in ubuntu feisty which is going to be released. Assertions should be turned on in the corresponding -dbg package but not in the production package.
Attaching a debdiff, with the obvious content. I use lyx for my everyday work several hours per day and simply cannot go on with assertions turned on, since it crashes when editing arrays for assertions related to the aspect of insets in mathed. This is the only kind of assertion I ever saw triggered in lyx, when using arrows to navigate tables.
Searching for "crash" on the lyx upstream BTS seems to confirm this feeling.
I opened a debian bug on this issue, # 410175, and e-mailed the two maintainers directly, but there is no agreement with debian on this issue, mainly the idea being that bugs should be solved and assertions not triggered.
I opened a lyx upstream bug on one of the most frequent crashes, but it's fixed in -svn, nobody pointed out how and where (it was just a "worksforme svn" kind of comment), the bug was obviously rejected, and nobody is going to dig lyx code to discover this, since 1.5 is coming out soon (1.5 will bring unicode support, and I guess it will have a very long alpha and beta stage, though this is only my feeling about it).
Given that ubuntu is going to ship 1.4.3, there is no reason to expect the situation to be resolved soon. The bug I reported is also in the ubuntu BTS here in launchpad, it is bug #68159. Nobody will ever look at it in ubunut.
In any case, I want to point out again that other distributions are shipping lyx with assertions turned off, that this is the default upstream setting, and that I am using this for my everyday work without problems.
This is all I can do, besides attaching the debdiff.