I’ve got 2 Aastra 480i phones, am using ulaw for connecting them to my VoIP provider, and the echo is bad enough that people on the other end of the line are complaining about it. I’ve contacted Aastra support about this and not gotten any help. Is it possible that the echo problems are due to something weird with ulaw? Is there any chance that using something like GSM or G.729 would do something about the echo problems?
Sorry, the above was poorly worded. I cleaned it up a little. 
i had some handset-generated echo problems on the 480i on firmware 1.3.0. upgrading to 1.3.1 got rid of them. what version are you running, and have you got any TX gains on the config files ?