I\'m having troubles logging into Magento\'s admin panel on one of our staging sites (it works 100% on our webdev servers and was working just fine not too long ago on the s
Having the specific error would help. A couple shots in the dark -
It's worth checking your rewrites. I've had issues moving from server to server where one of them doesn't have the rewrite setup correctly. if servername.com/index.php/admin works, but servername.com/admin doesn't, then you have a rewrite issue.
It could conceivably also be that the base_url is not configured for the right server. Did you change it when you moved the database over? See my answer at this post for details.