Some of the 4.30 versions of the BR Client DLL checks things in the wrong order causing update attempts to abort processing with an assertion failure. I am not aware of any versions of 4.31 that have this problem. This is a serious problem because the normal procedure for updating relies on the DLL to participate in updating itself, so when an attempt is made to update to 4.31 the 4.30 DLL prevents it.
Earlier versions of the 4.30 Client DLL did not have this problem. So by issuing the following command at a command prompt registry entries are removed that tell the client to use its latest DLL for conducting the update. This causes the client to revert to its original DLL for conducting the update:
reg delete HKCU\Software\ADS\BusinessRules!\CurrentClient
That has resolved the issue for most (possibly all) encounters of this problem. Unfortunately the command must be performed on the client workstations. But once it is fixed, the updating from the server proceeds normally.