Three of my 60+ categories load very oddly

[quickguitar]

Good call lat9, I do know that my database is in latin1_swedish.

However, my configure.php files have no reference to DB_CHARSET.

My original (1.3.x) was from a highly questionable reseller (Hit/Heritage Web Design)

[lat9]

That DB_CHARSET definition (set to either latin1 or utf8) was introduced in Zen Cart 1.5.0 and might have been missed on the upgrade.

I'd suggest a twofold approach:
1) Run the Db to Utf8 update script, converting all database tables and fields to utf8_general_ci collation.
2) Add the following statement to the database section of each of your configure.php files

define ('DB_CHARSET', 'utf8');

That's the default value being used now (and potentially part of your display issue) for PHP versions later than 5.3.

[quickguitar]

Thanks carlwhat + lat9

I read up on the utf-8 standard and will convert my databases soon here.

SEO plugin updated as well.