Please consider fixing this in 1.5.4+
It's hard to consider further upgrades, when there are still such bugs (well, incompatibilities) in previous version.
The core of the problem is that the column name in table mdl_choice 'release' became reserved word in Mysql 5.
There is a discussion
with a multitude o patches.
It is fixed in 1.6. The stated reason for not fixing this in 1.5x is that they are not fully tested. Well, I'd rather have a working non-tested version than simply broken one.
The only thing, that is needed for fixing latest 1.5.4+ is just to rename and replace the old 'release' with the new 'showresults' name in the scripts and in the database.
It shouldn't have any dangerous side-effects.
I'm attaching the module with this change. I have tested it and there are not any noticable problems.