When repeatedly execute complicated query through SQL
server 2000 ODBC connection in Vfox and VB. Custom
program stops respondoing and after long, long time
return the result set. In the same time I execute the
same query through query analyzer and I get the results
in resonable amount of time. (10SEC AGAINST 5-50
MINUTES). I tried the same query on any client machine
with different MDACs and OSes...

During that time SQL server is working perfectly with
other queries and performance stays the same.

When I restart SQL server service query executes in few
second more than through SQL QA which is OK

Query contains join on multiple tables with UDF call for
each record
UDF contains very complicated union query , i tried to
remove union but nothing gets better.

SQL Server 2000 sp2 and sp3 and sp3a