Well I think my firefox Deer Park (1.5) on Debian argues a lot with flash plugin if it is installed. Basically the browser hangs if I ever open a flash website. So this is what I did – ~/.mozilla/plugins/
removed all flash related stuff .so and .xpt from this directory and well I am a happy man to an extent.
I did not have problem using flash plugins with the prior version of firefox 1.0.7 Guess upgrades are not always good.