[development] losing value somewhere after validate.

[sime]

Hello.

I keep losing values that I modify in the 'validate' op of 
hook_nodeapi(). This occurs by the time I get to the insert or update ops.

It has to be something simple I am overlooking. I normally wouldn't 
hassle the list over such things, but I am starting to write bad code to 
compensate, so I need to work out what I'm doing wrong. It is a little 
hard for me to track the $node through core, so are there any 
suggestions about what I might be doing wrong, or where a problem like 
this can arise?

Kind thanks for any advice.
Simon

PS.
I have checked the nodeapi docs:
"validate": The user has just finished editing the node and is trying to 
preview or submit it. This hook can be used to check or *even modify the 
node*.

Also, I have double-checked that i am using a version of form.inc that 
is after this issue was fixed: http://drupal.org/node/63704