Ok this is definitely weird… I took a look at the backup of the database on the backend from Oct 2 and noticed that in the omeka_item_types_elements table that there was an important row missing in the upgraded database (namely, the row that gives ITM - Text the text descriptive field). So I added it back:
Now the field shows up under ITM - Text in the admin panel. However, it still refuses to display the text.
Meanwhile, in the old version of Omeka in the other folder, I changed the db.ini to the Oct 2 backup copy of the database and voila, everything works perfectly again. No “is not a valid URL” messages, no missing text data.
I still would rather us upgrade and use 2.5, but perhaps I should start by using this older backed up copy of the database before things went awry. If I do that, then I presume I will be prompted again to upgrade the database. If it doesn’t work then I guess I’ll reinstall 2.3.1.
As a side note, can someone tell me where the ITM - Text on each item should be pulling from, i.e. where’s the code that pulls it from the database? I need to check the fields.