Windows Media Player resizing cached video

Hi, this is a wierd one, and I'm guessing there's some kind of conflict with the thickbox js file, but I'm not sure. I have a page which calls up a wmv file in a thickbox, and it works fine when you first visit the page, but if you return to the page and try to view the video again, the video has expanded so it can no longer be viewed within the dimensions specified in the code.

The code that I'm using to call the video is:

<a href="#TB_inline?inlineId=VideoWMV&height=370&width=490" class="thickbox" title="RVSE video">This demonstration Video</a>
<!--start hidden video WMV -->
		 <div id="VideoWMV" style="display:none;">
<object type="video/x-ms-wmv" data="/products/RVSE2.wmv" width="490" height="370"> 
<param name="src" value="/products/RVSE2.wmv" /> 
<param name="autostart" value="true" /> 
<param name="controller" value="true" /> 
</object> 
</div>
<!--end hidden WMV video -->

Does anyone have any suggestions of what may be causing this? You can view the problem on this page:

http://www.cyrrus.co.uk/aviation-services-products.php by clicking on the RVSE Video Recording link in the first box.

Any ideas gratefully accepted!