As part of my efforts at trying to get the AsiMembershipProvider working, I have hit against problems because I've got old versions of certain referenced Asi assemblies.
This came as a surprise as I am using assemblies copied from the ASI\IMIS15\net\bin directory on an 15.1.1.3441 installation.
Just having a quick look through the assembly versions and I observe I have a mix of 15.1.1.2998 and 15.1.1.3441 versions. My suspicion is that because we upgraded from 15.1.1.2998, for whatever reason some of the assemblies where not upgraded.