I had to move my Moodle 1.8.4 with nWiki from MY-SQL to MS-SQL 9.0 and there is a problem with a field in the table mdl_wiki.
There is a field named "restore" and RESTORE look like is a reserved keyword in MS-SQL. Everything was jam in the installation process of the tables.
I had to rename the field with something else like "nrestore" in install.xml to complete the installation of nWiki.
But it was the only big problem and now it's working well, except it is now not compatible with the old stuff.