There seem to be at least a couple of issues to do with connecting to Rift. One issue is that some people can play fine during normal gaming, but once they get witin range of an invasion force laggy things start happening.

1) It is selective in that people from the same country on the same ISP can be effected differently. So one person is playing away in the middle of invasion chaos without problem, and another is unable to use abilities and usually gets disconnected, repeatedly if they try coming back in game whilst the invasion is still happening near their game location.

2) The Lag is first noticable by a lack of response to game commands: abilities, join public group etc. Later it can become evident that although the other characters and mobs have run around the screen, your version of game reality is 1-2min different from other peoples' with which you have alternate communication (ie MSN or being in the same room).

What might be going on?

The Rift Servers do seem to be sending out a lot more information during invasions, but why would some people be able to get the information, and others get disconnected? There have been comments about people who were fine when they first started playing but things then got worse.
Perhaps newer people are prioritised?
Perhaps lower level characters are prioritised?
Did a patch do something unintended to the process?

It is possible that the server is over calculating something that escalates exponentially when the number of people involved goes up?
Could it be trying to workout if people are in range of 20+ invasions forces and then trying to set up overlapping areas of 'join public group' that then end up in conflict somehow?

Do you get moved to a different area of the server when you are in range of an Invasion? If this is occurring, does this normally seemless process get stuffed over by something that grows exponentially when you have lots of people?