defender disables itself

[Francis]

i have vista home premium with all latest updates installed.

after some time, defender disables itself (exclamation mark next to
"defender castle icon' appears in task tray, saying defender is not running),
after some waiting also the tray icon disappears.

None of the users have administrator rights, but still it gets disabled.

 

[Francis]

this problem remains... just updated spyware codex (needed manual start of
Defender), one hour later it is suddenly disabled again.

is there ANYONE who has an idea what causes this

 

[robinb]

are you running windows live onecare?
if so, it disables Windows Defender when it does a scan because part of WD
is built into it
robin