[Zope] timing error in ZODB lock?

[Garry Hodgson]

i'm getting some funny behavior using a (separate from Zope's)
ZODB from External Methods.  after much thrashing, i've got my
application working.  however, every so often, when i click 
on a submit button that invokes an External Method, i get:

   Could not lock the database file. There must be another process
   that has opened the file. 

the odd thing is that if i click the browser "back" button, then
hit my button again, it works.  occasionally i need do this
back/resubmit thing more than once, but usually once suffices.

smells like a race condition to me.
has anyone else seen this, or have an idea how i can avoid it?

-- 
Garry Hodgson                   Every night 
garry@sage.att.com                a child is born
Software Innovation Services        is a Holy Night.
AT&T Labs                         - Sophia Lyon Fahs