WebControl Panel textbox Controls are invisible

[p]

I am using a tabstrip to have make tabbed user interface with webcontrols on
each tab. I control the visibility of the panels in the tabstrip postback
code but several textboxes are invisible (about half). I checked to see on
their properties and I cant see any problems with any textbox controls.
About half the textboxes are visible, as designed but the other half are
not. All the controls are bound to database fields and some are not null or
blank that are invisible, some multiline textboxes. A datagrid on a tab is
also invisible unless I explicitly set its visisbility, but other controls
(like checkboxes, DDLs etc all work). If I explicitly turn on an
"invisible" textbox in the tabstrip event, it works and I can see data?
There are no code errors and I also checked the html validatation and there
are no errors there either?

Any idea why the textboxes are not visible and datagrid?

Thanks In advance
P