'./wikidb/searchindex' is marked as crashed
and should be repaired
I experienced this same behaviour when upgrading from MySQL 3-4 and from
MediaWiki 1.6->1.11. I think I've fixed it (hopefully permanently) by
dumping the table, then dropping it, then re-creating it again. I found
that repairing the table worked, but the error would re-occur. Hope this
works for you.
Peter