2.5.2 -> 3.0.3 ZenPack removal problem

Hi,

I'm attempting to upgrade a test 2.5.2 box (CentOS 5.5 x86) to 3.0.3, but one of our home grown ZenPacks is stopping the upgrade as it's not compatible. The problem is that I can't uninstall it. I've tried via the GUI which does nothing and the command line:

$ zenpack --remove=Device_Server_Linux_Class

ERROR: zenpack command failed. Reason: ObjectNotFound: object <ZenPackManager at ZenPackManager> was not found on <ToOneRelationship at manager>

I've also tried via zendmd:

$ zendmd

<snip>

>>> dmd.ZenPackManager.packs._delObject('Device_Server_Linux_Class')

2012-01-23 09:50:38 WARNING OFS.Uninstalled Could not import class 'HttpMonitorDataSource' from module 'Products.HttpMonitor.datasources.HttpMonitorDataSource'

Traceback (most recent call last):

  File "<console>", line 1, in ?

  File "/opt/zenoss/Products/ZenRelations/ToManyRelationshipBase.py", line 79, in _delObject

    self.removeRelation(obj)

  File "/opt/zenoss/Products/ZenRelations/RelationshipBase.py", line 109, in removeRelation

    self._remoteRemove(obj)

  File "/opt/zenoss/Products/ZenRelations/ToManyContRelationship.py", line 177, in _remoteRemove

    rel._remove(self.__primary_parent__)

  File "/opt/zenoss/Products/ZenRelations/ToOneRelationship.py", line 91, in _remove

    raise ObjectNotFound( "object %s was not found on %s" % (obj, self))

ObjectNotFound: object <ZenPackManager at ZenPackManager> was not found on <ToOneRelationship at manager>

>>>

On both this box (and a yet-untouched prod box) I can't even select the ZenPack in the GUI as it thows an error. So restoring from backup isn't much of an option as it's previously broken.

•   Module zope.tales.tales, line 696, in evaluate
  URL: file:/opt/zenoss/Products/ZenModel/skins/zenmodel/viewPackDetail.pt
  Line 135, Column 4
  Expression: <PythonExpr container.dmd.ZenTableManager.getBatch(tableName,objects,sortedHeader='getPrimaryDmdId')>
  Names:{'container': <ZentinelPortal at /zport>, 'context': <ZenPack at /zport/dmd/ZenPackManager/packs/Device_Server_Linux_Class>, 'default': <object object at 0xb7f15538>, 'here': <ZenPack at /zport/dmd/ZenPackManager/packs/Device_Server_Linux_Class>, 'loop': {}, 'nothing': None, 'options': {'args': ()}, 'repeat': <Products.PageTemplates.Expressions.SafeMapping object at 0xac866cc>, 'request': <HTTPRequest, URL=http://lqzen01:8080/zport/dmd/ZenPackManager/packs/Device_Server_Linux_Class>, 'root': <Application at >, 'template': <FSPageTemplate at /zport/viewPackDetail used for /zport/dmd/ZenPackManager/packs/Device_Server_Linux_Class>, 'traverse_subpath': [], 'user': <PropertiedUser 'admin'>}
•   Module Products.PageTemplates.ZRPythonExpr, line 49, in __call__
  __traceback_info__: container.dmd.ZenTableManager.getBatch(tableName,objects,sortedHeader='getPrimaryDmdId')
•   Module PythonExpr, line 1, in <expression>

Anyone got an idea of how to get round this. I've noticed a few similar posts over the past year or two, but they don't seem to end in a solution.

Thanks in advance!