Could anyone help fix this error quickly?
 

Whenever I try and go to my site, I get this error:

vBulletin datastore error caused by one or more of the following:

1. You may have uploaded vBulletin 3.5 files without also running the vBulletin 3.5 upgrade script. If you have not run the upgrade script, do so now.
2. The datastore cache may have been corrupted. Run Rebuild Bitfields from tools.php, which you can upload from the do_not_upload folder of the vBulletin package.

Fatal error: vBulletin datastore cache incomplete or corrupt in /includes/init.php on line 170

Ok, I'm assuming that you have been running 3.5.4 quite happily with no problems. If not, then you need to run the upgrade scripts as per point 1.

In your vB Zip file there is a do not upload folder. Upload the file tools.php from that folder to your site and access the page. Run the rebuild bitfields script, then delete the file from your server.

Rebuilding the datastore options from tools.php didn't fix it. :(

Any other ideas?

Not a clue after that.

/me recommends checking original files are uploaded, and if persists using a support ticket via the members area.

Re-upload the files in text mode, not binary mode. You might have a corrupted file or files if rebuilding the datastore didn't work. Just a guess here. ;)