I ran into a similar issues myself with Write-Once after upgrading to 7.5, mainly affecting only the webaccess /selfservice
I contacted LANDesk regarding this because it was really buggy (it was wiping the "write once" data after saving!) and they suggested this:
For each action, create two of the same window, one window with all "Read/Write" and the second window being "Read Only"
*Setup the first window with "Read/Write" capabilities, this will be the intial window for each action
*Setup the second window with "Read Only" capabilities, after saving this will be the window displayed that cannot be modified
Next, setup a window view-rule:
*Object State: NEW, display the window with "Read/Write" protection
*Object State: UPDATE, display the window with "Read Only" protection
Hopefully this helps!