you can edit invision db through phpmyadmin, i just reuploaded a backup onto a fresh install on gtachat.com (server got hacked) and all the posts and such are back.

goturuge, i would suggest backing up your entire database, and then attempting to edit it to allow access, or simply reinstall the forum and upload the sql dump.

i would also suggest finding a host with fantastico, as that allows invision along with many other scripts to be installed much quicker than it is to upload and configure them manually.