A B767-300 dumped fuel and returned to their departure airport when they received recurring LE FLAP ASSYM EICAS messages; first upon flap retraction and; after self correcting; again in climb.

Narrative

On flap retraction the needles stopped between 1 and up and the LE FLAP ASYM EICAS message was displayed. We continued on the departure transition ground track while we accomplished the associated checklist. We then contacted Dispatch and Maintenance Control. During this initial contact the flap needles moved to UP indication and EICAS extinguished. Flap air speed limits were not exceeded.We were then cleared by ATC to climb to FL280 at normal climb airspeed. While in the climb the EICAS message re-illuminated with the same position indication on flap indicator. We immediately slowed to 230 KTS and requested descent below FL200. Several attempts to establish contact with Dispatch and Maintenance Control including via SATCOM were unsatisfactory.We elected to return to our departure airport; requested emergency equipment but did not declare an emergency. At some point during descent the EICAS message extinguished again and flaps 1 was selected. In this configuration the slats remained extended. We dumped fuel and then conducted a normal approach and landing.