After taking a backup of a site contentDB, all of a sudden the siteactions menu disappeared even for the Site Collection Administrator. However, as a administrator, you could still navigate to view all content directly /_layouts/settings.aspx. This may happen when the site gets locked to 'Read Only' during the back-up process. You might want to test this with the below two commands
stsadm -o getsitelock -url http://www.shopsharepoint.com
This should give a SiteLock Lock='None'. If it shows somethig like SiteLock Lock='read Only', then you might wnat to fix it with the below command.
stsadm -o setsitelock -url http://www.shopsharepoint.com -lock none
This will unlock the ReadOnly lock and should work fine as usual. try to do a iisreset to avoid caching.