[Seaside] Seaside, Omnibase, OmnibaseSupport - markDirty failing

[Wilkes Joiner]

I'm learning to use Seaside with Omnibase and am having some issues. 
I'm getting a "ODBError: Object is not persistent or is a part of
composite persistent object" when calling markDirty on an object.

Here is the setup for the app.
I'm using a custom Session class, BLGSession, which is a subclass of
ODBSSession.
I have one domain object, BLGPost, and two components.  One for
listing posts, BLGPostList, and another for creating and editing them,
BLGPostEdit.

BLGPost inherits from ODBSPersistentObject.  It has a body attribute
with the following setter:

BLGPost>>body: anObject
	body := anObject.
	self markDirty.

The edit component is causing the problem.  When I call it to modify
the body attribute of a Post I get the "not persistent" message.

BLGPostEdit>>post
	^ post isNil
		ifTrue: [post := BLGPost new]
		ifFalse: [post]

BLGPostEdit>>renderContentOn: html
	html form:
		[html paragraph:
			[html label for: 'post_title'; with: 'Title'.
			html break.
			html textInput on: #title of: self post].
		html paragraph:
			[html label for: 'post_body'; with: 'Body'.
			html break.
			html textArea on: #body of: self post].
		html submitButton callback: [self answer: self post]].

I've tried many variations and permutations of this, but can't seem to
get this to work.  Anything obvious that I'm missing?  Is my approach
off?

Thanks,
Wilkes