Invalid Boolean Script Error

Hey guys. I don't want to give away my current project so I wont say much other than the code and my problem.

In the following script I get this error:

Error:

6:07:26 PM - Error on line 13: String was not recognized as a valid Boolean.

This is the script. No idea what is causing it, other than perhaps there is too many phrases.

Script:

#This is the Control script. Theta's functions all  
#are started by this script. It must be running to 
#allow Theta to operate. Kill this script to slowly 
#stop Theta. 

#Variables
$returngreeting = 0
$reply = "error"

:loop
$spoken = Waitforspeech( 120, "hello Theta", "good morning Theta", "good afternoon Theta", "good evening Theta", "good night Theta", "hey Theta", "Theta", "bye Theta", "see you later Theta")
#Error is on next line
if ( $spoken = "hello Theta" OR "hey Theta" OR "Theta" )
ControlCommand("Script Manager AI", ScriptStart, "Greeting" )
$spoken = "error"
Elseif ( $spoken = "good night Theta" OR "bye Theta" OR "see you later Theta" )
ControlCommand("Script Manager AI", ScriptStart, "Leaving")
$spoken = "error"
Elseif ( $spoken = "timeout" )
saywait("I missed that")
$spoken = "error"
endif 

$timeout = $timeout + 1
if ( $timeout = 120)
ControlCommand("Script Manager AI", ScriptStart, "Leaving")
endif

Sleep(500)

Goto(loop)

Thanks for the help. I'm sure its a simple mistake. Maze