BuddyPress.org

Why did you not simply upgrade the present installation to latest WP then after upgrade BP, probably safest as incremental version updates rather than jump to 1.5 when it sounds as though you might have been on a pretty old version even a 1.1 stream.

It may be the case that the present new version of BP needs to run it’s DB upgrade script, if it still can, not sure of the consequences if you install and set up 1.5 then import old db tables.