In the DB where I'm storing my data, I have flags on which records need
to be processed through Notification Services, to make it easy for my
EventsQuery to go grab them. These flags are set up the chain by the
application. After processing, using the PostQuery argument, I was
going to reset the flags. My question is - is there a chance between
the EventsQuery grabbing the data & the PostQuery resetting the flag,
would my app be able to modify the flags - making my notifyprocessing
flag get off kilter? Does EventsQuery & PostQuery run in one
transaction to ensure data integrity?

Answering my own question here.........from microsoft....

"The postprocessing query runs in the same transaction as the
event-gathering query."

http://msdn2.microsoft.com/en-us/library/ms172487.aspx