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Old url error detected by DMOZ.
Site removed from DMOZ.
Google directory updated from DMOZ.
Url change in DMOZ requested.
Url changed in DMOZ.
If that's what happened, then you should be back in the Google directory next time it updates.
It has also been known for Google to roll back the Directory index to previous RDF dumps.
Wait till the next couple of Google Directory updates before worrying too much, besides DMOZ listings and inclusions are generally not nearly as important as they used to be to Google rankings.