InfoPath Dev

Hi, while trying to Open infopath form through secured site,i am getting following error
"Infopath cannot open the selected form because of an error in form's code
The form code could not be loaded because of security restriction
the assembly does not allow partially trusted callers"
This is the problem with Infopath 2003 SP2 and above
Can anybody suggest

Welcome to our forum. There are a number of different possible issues. First thing, try the steps in this post:
http://www.infopathdev.com/forums/topic.asp?TOPIC_ID=3022&SearchTerms=primary,interop

If that doesn't work try this:
http://www.infopathdev.com/howto/tutorials/default.aspx?i=010d815fd99f491d896f2e9a02d6c0ab

i am really struggling with few errors
Ofcourse strange thing is above error got cleared when 2007 is installed.
Another Error:
"Error:Infopath cannot submit the form,because it contains validation error.Errors are marked with either a red asterik (required fields) or a red,dashed border (invalid values)".
This form works well in few machines with same data, but gives problems in few machines, what might have went wrong

We are tracking a few bugs on security warnings between InfoPath and IE. The likely reason your error was cleared is that the InfoPath 2007 install migrates your form cache which essentially resets some stuff (too complex to explain here).

For your validation errors question, InfoPath enforces validation for submit so the server data is always valid. This error means that either some fields have invalid data or are blank but should have data. If you don't see the red error markings, then the error is likely in a node not on your view.

You'll have to explain more the exact scenario on how you can reproduce this error displaying on some machines and not others. If the form is filled out in the exact same way, and the code is running in the exact same way on all machines, this shouldn't happen.