See this post for additional information. Also, be sure to paste your code as preformatted text instead of a blockquote.
I have also found issues using the TransactionManager with documents other than the current DBDocument. Instead, try creating a transaction manually:
famdoc = doc.EditFamily(family)
t = Transaction(famdoc, 'Describe your transaction')
t.Start()
# Do stuff here
t.Commit()