18 mph 1/2" pedal depression...?

[taylorkevin]

Anyone have any ideas on what would cause my pedal (98 ranger XLT 10" ABS) to lose about a half inch everytime I slow down and hit around 18 mph? Sometimes after this happens, the ABS turns off (light comes on) and brakes work fine after that, just no ABS...

Possible ideas... just need bled? speed sensor? new brake cylinder? Rather not take shotgun approach and just take a guess if someone has had a similar problem or knows what this is...

Thanks in advance!