Annoying Flash IDE: "error opening URL" for help

Hi folks. I have an annoying intermittent problem when using the Flash CS3 IDE on my MacBook Pro. The problem is help works sometimes, but frequently and without warning I get “Error opening URL” message from Flash. It doesn’t seem to be a network problem since even when not on a network sometimes I get this error and sometimes it loads the help properly.

Some version info:

MacBook Pro 2.5 GHz Intel Core 2 Duo, 4GB RAM, OS X version 10.5.5
Adobe Flash CS3 Profession version 9.0

Details to reproduce:

Open any FLA and/or .AS file (these are all AS3 projects). Highlight a keyword (already being displayed in blue by editor indicating it is a reserved word/known class). Press F1 for context sensitive help. About 50% of the time it works, the other half it displays “Error opening url”. Once that error is received, no help works.

Any suggestions? I’ve already reinstalled the software from distribution disk. TIA