The web.xml deployment descriptor for ColdFusion MX 7 may not have attribute at all in either Server Configuration or Multiserver Configuration. If this attribute is absent, then the J2EE session length will default to 20 minutes.

Provided that your ColdFusion MX 7 application is configured for ColdFusion (not J2EE) Session Timeout exceeding 20 minutes, then you may get the error "Session is Invalid".

This is not quite the same the known issue in CFMX 6.1 described in Technote 19109, although the ultimate cause and solution are the same. To resolve this in CFMX, add a session-config node to web.xml that has a child node for session-timeout attribute and then enter a value in minutes greater than the length of any CFMX session timeout. Just look at the 6.1 technote above or 6.1 web.xml to view how the node should be created. There is some discussion of the position of the session-config node being positional, so to be on the safe side, enter the node in the same place it was in CFMX 6.1, that is right after the servlet mappings and before the welcome file list.

There has a been a great deal of discussion of this problem at Crystal Tech ISP, and I know that the problem was solved there on at least some servers, so perhaps it hasn't been pushed to all servers yet.

There is a fair amount of speculation for a code workaround, which I doubt will be very useful, and that anyone seeing the problem probably still hasn't followed the recommendation to create the session-config/session-timeout node properly with a time exceeding any CF session timeout.