Behavioral Change on IE7 can affect Outbound access through ISA Server 2006 that is using Redirect on a Deny Rule
However, there have been some changes in IE 7, and presumably IE 8, that might cause some unexpected things to happen when you use these kind of redirect rules.
Yuri Diogenes describes what happens in this scenario over at:
Thomas W Shinder, M.D., MCSE
Sr. Consultant / Technical Writer