We have used Think Pascal for years to introduce students to programming,
once it was impossible to run the interpreter Macintosh Pascal on systems
with 32 bits addressing.
Symantec posted (n  a public directory) a 4.5 unsupported version of Think
Pascal. When system 8.5 came out, Think Pascal had also problems! A patch
(ValidDate) was supposed to permit the use of the compiler with the new
system. However, this patch seems to be only effective under system 8.5.x
but under 8.6 as soon as  a project is closed and another one opened or
even after quitting Think Pascal and reopening it, the computers freeze (we
tested iMacs, PM8500, PM 6100, PM 5200, PowerBook G3 all under 8.6 french;
all machines exhibit the same behaviour: freezing after the second launch
of Think Pascal).

The new academic year begins at the end of the month (september) and we
need a solution! Shifting to CodeWarrior seems a little bit too complicated
for our students...

I really don't know about a quick solution, except for downgrading to a
previous version of the MacOS. There is a project udner way to port the
Free Pascal Compiler to the MacOS, but it's still far from complete (it
will easily take still half a year, if not more).

Jonas