If you look at section 19.5 of the datasheet for the 18F4620 you'll find this:
When reading the Port register, all pins configured as analog input channels will read as cleared (a low level). Pins configured as digital inputs will convert as analog inputs. Analog levels on a digitally configured input will be accurately converted.
So if you do a TOGGLE on a pin which has NOT be set to digital it will read '0', the bit will then flipped to '1' and written back to the port. Next time you do that TOGGLE it will again read the bit as '0' (even though it was previously set to '1'), flip that bit to '1' and write it to the port. Ie. it will never toggle it low because every time its told to toggle the bit it's read as low and gets toggled to high.

Page 224 in the same datasheet shows how to set ADCON1 up in order to configure the various pins as either analog or digital. And then there's the compartor as have been pointed out, see page 234. However for the 18F4620 the comparators are OFF by default so you strictly speaking you don't need to turn them off again. ALWAYS make a habit of checking IF you need to turn comparators off and/or enable digital mode on the pins you're using and HOW to do that - not all chips are the same.

/Henrik.