Also, upgrading from 2.4a3 (with extensions installed) to 2.4b1 (with no extensions) would have the same effect - there is simply no support for restoring older versions of the extensions when uninstalling (and upgrading from 2.4a3 to 2.4b1 is actually the same as uninstalling 2.4a3 first).
this appears to be exactly the case with me, I run both the 2.3 and 2.4 branches on the same box... and I upgraded py2.4a3 to py2.4b1. the funny thing is that when I installed Py2.4a3 some time back all went well. this time the installer restored the last setup options (except the setup dir... I do not use %systemdrive%\python24) and removed ALL file associations, including for Py2.3.4, and messed up the overall python registry configuration! (which is quite odd....).