NullPointer Exception on mouseover tooltip

Hi,
I'm getting a NullPointerException on a chart whenever I add anything to the mouseover tooltip text to the Value Series. It works fine on other reports, but for some reason this particular report doesn't like it.
This is BIRT 3.7.2, and I verified the only change to the report XML was the single line change from

...
  <Text></Text>
...

to
line change from

...
  <Text>"Example";</Text>
...