postgis cyclic performance hit

[Richard Duivenvoorde]

Hi List,
I'm running a developer machine windows, postgis/mapserver.

It contains one small layer (50 points).

If I run a ogc-mapserver request (in a browser) for an image of those 
points, the performance behaves strange:
- about 10 responses ok: about a few hundred milliseconds
- then one VERY slow one: about 4 seconds
repeating that every 9-14 requests

created gist index on geometry layer
created btree index on id column
gave postgresql some more memory

still the same result.

QUESTION:
- any people running mapserver/postgis on a windows machine and having 
good response times
- somebody a clue to this cyclic 'bad response time' behaviour?

Thanks

Richard Duivenvoorde