openoffice.org problem

I am getting the following message when I try to open a pdf file that I had saved on my desktop or open the program to work

either another instance of OpenOffice.org is accessing your personal setting or your personal settings are locked.
simultaneous access can lead to inconsistencies in your personal settings, you should make sure user 'dradheshwar' closes OpenOffice.org on host 'ds-macbook-pro.home'.

do you really want to continue?

yes no

I removed the previous download of OpenOffice.org from my computer and installed it again. The problem persists.
How to resolve, can you help?

Many thanks.

Damu Radheshwar