Problem with Lyx multirows

Hi,
I'm in the process of writing my thesis in Lyx, but I'm pretty new to it. I've
been having some problems with creating multirows in tables. I tried to follow
the instructions from http://wiki.lyx.org/LyX/Tables, but can't get it to work
in my own lyx document. Whenever I want to watch the PDF view an error saying
Undefined control sequence pops up with the following description:

\multirow
{2}{2.5cm}{multi row} &  &  &  & \tabularnewline
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., \hobx'), type I' and the correct
spelling (e.g., I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
I have attached a lyx file with a table and the code that I tried to use. Any
help would be much appreciated.
Thanks,
Jacob Larsen

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problemwithmultirow.lyx
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