Rails - Mar 2006 - Private method gsub Error

Hi,
I keep getting this error when trying to use a condition in one of my habtm.
I''ve used conditions in habtm before in other projects and they work
fine. Now I''m getting this:
private method `gsub'' called for ["user_id = ?",
"1"]:Array

This is what I''m doing.
has_and_belongs_to_many :TenSpeed, :class_name => "Bike",
:conditions =>["gears = ?","10"]

Any ideas why I would be getting the ''private'' error?

Cheers,
Eric Goodwin