suddenly can't log in and password reset doesn't work

[Lynne]

You don't have to have the strikes system on (that incredibly annoying idea you talk of). Disable it when you can next get into your admincp.

1. Download a copy of the vBulletin zip file from vBulletin.com (if you don't already have it).
2. Once you have done so, extract the contents and navigate to the do_not_upload folder, from this folder select the file named tools.php and upload this to your /admincp/ directory on your board (via. FTP).
3. Type in the path to the file in your address bar, e.g. http://www.yourboard.com/forums/admincp/tools.php
4. Enter the details required.
5. You will then be presented with a list of options, you'll need to look for one which says 'Reset Cookie Domain' and follow the on screen instructions.

Once this has been done, remove tools.php from your AdminCP folder.