AS2, Adobe CS5 - strange bug while trying to start SWF at random frame

Hi folks…thanks in advance for reading. I’m stumped.

I have a 1400 frame SWF which should always begin on a random frame. Here’s the code I’m trying in frame 1:

randomnumber = Math.floor(Math.random()*1400+1);
gotoAndPlay(randomnumber);

The trouble is, the random number only seems valid up to approximately 650 - any random number generated that’s higher than ~650 will begin playback AT 650. To test what’s going on I added two dynamic text fields, one showing the randomnumber value and the other showing _root.currentframe. Every time I run the SWF, the two numbers should start at the same value (randomnumber) and the _currentframe value should increment by 1 with every passing frame. And that’s exactly what happens if the randomnumber is below 650. However, randomnumber values greater than 650 display properly in the text field linked to that variable, but the _root.currentframe value and actual playback begins at 650, regardless of the randomnumber generated. So rather than randomly beginning playback at any of the 1400 frames, the randomizer can only begin playback at any of the first 650 frames. Please help - what am I missing?

Thanks VERY much.