Thanks - I will have another go! So far the only time I have got Chieftains to move is the Afghan map with no enemies, so maybe I am missing something. Having got the game just a couple of days ago from Steam via Bundlestars, I think she's up-to-date; the last enabled item in the Game Updater table is 'Game Update 4.08' and I can't find a later patch for Steam versions.
Edit - checking the main menu screen, it says I'm on version 5.81, Jul 15, so I think that's up-to-date. Tried again on the Sokolovo map, mixed force of M113, M60 and Chieftain platoons; the US kit moves off smartly, but with identical order types, boththe Chieftain platoons creep forward a few yards then stop. Changing order type between attack and move does not get them going. Weird.
Edit - finally got the Chieftains moving in Shilovo...
...but they were slow to make a start and very slow to move when they finally did decide to get cracking - slow even for Chieftains. Heck, the Chieftain in this clip at 6:32...
...is moving faster backwards! Also they moved very hesitantly. Checked that time compression was at/about 1.0. There is a BIG difference in speed and orders response time between M60s and Chieftains in the same terrain, in a similar tactical situation and with the same commands - is this what you are seeing. Frenzi?