I have been getting this error occasionally when installing or upgrading an RPM. This morning's example was upgrading squid-2.2.3 (from an external provider) to squid-2.2.STABLE4 (from the RedHat updates section). "free list corrupt (7626952)- contact support" The files appear to all get installed, but "rpm -qa" shows the old version number, so it must be bailing out before it finishes. Removing the old one, and installing ("rpm -i") the new one, gets the same error.
Try rpm --rebuilddb and repeat the command that failed. Usually this problem occurs when rpm is attempting to install 2 versions of the same rpm in the same command. Please reopne the bug if the problem persists.