This has happened to me in two playthroughs. After the initial time speaking with Zaleskar (I don't think it matters which character talks to Zaleskar, I don't think it has to actually be Ifan the first time), Ifan can no longer initiate conversation with Zaleskar. If you are using Ifan as your barterer, for example, you must initiate conversation with a companion, and then switch in the vendor menu.
What actually occurs is, when controlling Ifan and clicking on Zaleskar with the speaking bubble cursor, Zaleksar's character turns to Ifan, and both get the talk bubble icon above their heads, and a sound plays, but no dialogue opens, and then the non-existent dialogue "closes", terminating the talk bubbles, and resetting Zaleskar's position.
