Can you explain a little more about the source of the .iAvatar. For example, is it a non-standard character you imported via 3DXchange? Also do check that you have iClone 7 updated to the latest version which is 7.73. This is important because if you have an iAvatar created in 7.73 but you are using 7.71 then the character can give an error when you try to load it.
If possible please post the .iAvatar file and we can test it. If you don't want to post it publicly, just send me a private message with the link. Thanks.