Importing an old database

I recently had a problem with my WordPress blog that left it inaccessible- pages showed up as blank. Since I was planning on moving to a new host anyway, I installed WP on the new host, copied over my wp-content, but had problems moving the database. That allowed me to continue adding new posts, although my old content was still inaccessible.

Since I couldn’t get the database to import to the new host, I thought I would try reinstalling WP on the old host and exporting from the dashboard. The install went fine, and I was able to access the dashboard, but none of my old posts were accessible. When I checked the database, I discovered that the old posts were still there, but the reinstall had created a new set of tables, with a different prefix.

I tried renaming the tables, but the structures are different, so I assume that the old tables are a different db version, even though the db_version in wp_options is 18226. My question is whether there’s a utility or script that would take an old wp database and upgrade it to the current version? Or is there another way of doing it? The old database has several thousand posts and comments, so I don’t want to lose it.

Thanks in advance for any suggestions!