Label decorators and library files

["sxk129" <sxk129@xxxxxxxxxxxxxxxx>]

I have written a label decorator as part of a plugin I am coding.
For some reason, jar files in the workspace which are included in the Java
build path libraries are decorated only the first time they are displayed.
Even if I explicitly fire a labelProviderChangedEvent with the resource
associated with the jar file, there is no callback to my decorator.
For all other files in the project workspace, it works fine.
I tried debugging into Eclipse UI code, but after many levels of
abstraction, it simply got too dense to be meaningful.
Any ideas why this is happening?
---
Thanks,
Sunil