Thread:Project:Support desk/Uploading files require create page permissions/reply (11)

What 109.155 says is true, except when  is in use, as the original message say.

Even if you upgrade, you'll still have the same problem. Maybe Extension:Lockdown may help on that, restricting page creation only for certain namespaces (and not the main one), but IMHO, this kind of restriction seems a bit weird.

Another option is Extension:AbuseFilter, where you can define rules for that.