If you have in your hostd.log something like this:
Nov 07 21:19:12.648: Worker#23| Caught signal 6 -- tid 31543
this can be related with update(upgrade) of host OS.
To be sure that your downgrade of glibc worked - check the size of libc-2.5.so. I got an issue on downgrade (even with --oldpackage rpm was not willing to replace a libc), and that's why I lost some hours trying to figure out what is going on. So, be sure to check the size of the files after downgrade. It can save you some hours :)