[thelist] image disappearing problem

[Wil Cone]

I'm hoping someone can point out what I'm doing wrong on this page:

http://www.inaridesign.com/projects/test/test.htm

It's supposed to work like this:

Click either the disclosure image or "Period Summary:" and 1) a table of
data appears and 2) the disclosure image swaps out (it now points up).
Click again and the page reverts to it's original state. 

I'm getting a weird problem in IE6 & Opera7 where the _very first_ click
will cause the disclosure image to disappear completely rather than swap
with its up-arrow version. If I put any error-checking (elementX.src)
alerts into the code, the problem disappears, so I'm having difficulty
troubleshooting this...

Any help would be greatly appreciated.

- Wil