Source : http://www.dotnetnuke.com/Community/F...

On the Host > SQL page, try running the following check the run as script checkmark:

UPDATE dbo.{objectQualifier}Tabs
SET    IconFile = REPLACE(IconFile, '~/images/', '/images/')
    ,  IconFileLarge = REPLACE(IconFileLarge, '~/images/', '/images/')
WHERE  IconFile LIKE '~/images/%'

Then go to Host > Host Settings and click Restart Application.