Had this issue for a while [parse error when banning user]
 

We get this error when we delete a user: have done since day one really.

Any ideas what is causing this please ?

Most errors regarding "eval()'d code" comes from a plugin. What is on line 2315 of your class_dm_user.php file? That will give you a hint of what the error is from.

Line 2315

($hook = vBulletinHook::fetch_hook('userdata_delete')) ? eval($hook) : false;

There you go.... it's a problem from a modification that has a plugin that uses the userdate_delete hook location.

okey dokey... so hmmm... how do we find out which plugin is the issue... or...

Use the tried tested and trusted method of "process of elimination" by disabling ?

Yep. Or, you look at your list of plugins to find the ones using that hook location. I doubt there are many.