named scope - wrong number of bind variables

I have the following named scope:

named_scope :report_search, lambda { |search|
  {
    :conditions => ["rep_name like ? or rep_id like ? or rep_symbol like ? or rep_issue like ?", search]
  }
}

When i run it, I get the error message:

wrong number of bind variables

I would appreciate it if somebody could help me figure out wht's wrong with the code.

Many thanks