Welcome to the Forum! Just to let you know, the NLSC Issues section is for issues related to this website itself. Any questions about the game belong in the specific NBA Live sections. Also, please try to avoid posting in all caps. Thanks.
This is a known issue with the Xbox 360 and Playstation 3 versions of NBA Live 08. Unfortunately, no official fix was released. If you can avoid making substitutions through the pause menu, you can usually avoid this issue as well though that's obviously not always convenient. Unfortunately the only way to resolve the issue once it occurs is to restart your system, as you've already discovered.