[Zope] ImportError: cannot import name Persistent

[John Ziniti]

One of my Python Products is not working.  It fails with the
above error when trying to "from Globals import DTMLFile"

File "/home/local/opt/Zope-2.4.3/lib/python/OFS/Application.py", line 
563, in import_product
product=__import__(pname, global_dict, global_dict, silly)
File "/usr/local/zopeinstancehome/Products/XXX/__init__.py", line 2, in ?
from XXX import XXX manage_addSNPSetForm, manage_addSNPSet
File "/usr/local/zopeinstancehome/Products/XXX/XXX.py", line 11, in ?
import YYY
File "/usr/local/zopeinstancehome/Products/XXX/YYY.py", line 13, in ?
from Globals import DTMLFile, HTMLFile, InitializeClass
File "/home/local/opt/Zope-2.4.3/lib/python/Globals.py", line 95, in ?
from Persistence import Persistent, PersistentMapping
ImportError: cannot import name Persistent

Other products which do exactly the same thing are working fine.
This product was also working earlier today.

I've tried the "import ZODB" trick, but it doesn't help.

Any ideas?

Thanks,

John Ziniti