When you installed PG 7.1 rather than PG 7.2 did you remember to kill off the old postmaster, get rid of all the files left behind from PG 7.2, etc etc etc?
The "SearchSysCache" error you're getting is internal to PG and my first guess is that something's messed up in your install. Be sure, too, that you're running PG 7.1.3 (the last of the PG 7.1 series) not PG 7.1 in order to make sure you've got the last bug fixes to get into PG 7.1.
