Search form block not showing in IE7 and IE8 Search shows fine in chrome but not in IE8- looking at the code the DIV block-search-form simply isn't there. This occurs in different themes and also if I change where search should be displayed. 

I'm on a fresh install of 7.12 with commerce kickstart, internationalization and other pretty standard modules.

Any ideas?
Judging from your commments it's a permission issue. To solve it select People -> Permissions from the admin menu (or use the path admin/people/permissions) then look for Search and give 'Use search' (and possibly 'Use advanced search') permissions to the roles you want.