Are these both PG sites, both Oracle sites, one of each???
Installation requires the execution of some RDBMS-specific queries, so it really helps to know which is being used as a bug in one won't necessarily be mirrored by a bug in the other.
If they are both running the same RDBMS, then something else is different. Have you closely checked your server log for problems in installation? I won't guarantee that all problems will result in a message to your browser. They *should* of course, and if you find such a problem let us know so we can look into doing a better job of reporting it.
