Question on confusing behavior

Today, I told someone the syntax for "count" without thinking, and
got it wrong - and in so doing, I found some interesting behavior.

select count('table.fieldname');

works. however...

select count('table.fieldname') where table.fieldname='something';

not only barfs, it kills your connection to the back-end. Then...

select count(table.fieldname) where table.fieldname='something';

works fine.

So, if the field name to count is enclosed in ticks, it works if there
is no where clause, but not if there is a where clause.

Now I'm not an expert at SQL, so I realize that it could be because I
used totally illegal syntax. But, then I'd think that postgres would
barf consistantly. Anyone care to enlighten me as to what's going on?

steve