We are about to release version 1.0.2 RC3 which includes full compatibility with MW 1.9.0.
The only outstanding issue is the 'Session lost' error reported above. Since we cannot duplicate this in-house we are working with some of our users to troubleshoot this.
Once we duplicate and fix this issue, we'll be launching v1.0.2 RC3. An updated changelog can be found here:
http://www.nuhit.com/products/vbwiki-pro-changelog.html
Notice that the fixes and support for MediaWiki 1.9.0 apply to both vbWiki Pro and vbWiki Standard.
We have vbWiki Pro 1.0.2 RC3 working with MW 1.9.0 in our site:
http://www.nuhit.com/wiki/Special:Version