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Is it the persistence of the old articles that you are wondering about or the persistence of the old layout?
First, XOOPS caches the info your modules output. You may need to reset the cache on the offending module to zero. You can also try to update the offending mod and even the system ( admin|modules|system).
You can also clean out the contents of the templates_c directory. Sometimes that seems to kludge things a bit.
Just some thoughts, seeing that no one else had responded. Not sure it's worth the paper its printed (?) on...