Performance degradation on query analysis

[Stepan Migunov]

Hi
We have an issue with our production environment - from time to time we notice 
a significant performance degradation for some queries. The strange thing is 
that the EXPLAIN operator for these queries takes the same time as queries 
execution (5 minutes or more). So, I guess, the issue is related to query's 
analysis but not data extraction. Is it possible that issue is related to 
SYSTEM.STATS access problem? Any other ideas?