I've avoided this problem for now by disabling xapian on my Debian
Squeeze hosted roundup installation. So I lose relevance driven
keyword search but it seems to me that roundup derives little 
benefit from this anyway since it typically sorts the results
according to its own rules.

I'm no IR expert. Am I missing something here?

What is the benefit of xapian indexed search in roundup compared
with the old rdbms indexer?