I've uploaded my changeset to two different sandboxes this morning, but I'm still unable to deploy them. I keep getting the message:

Change Set Unavailable
This change set is not currently available. Recently uploaded change sets may take up to 30 minutes to be available for deployment. Please wait 30 minutes and try deploying your change set again. 

It's been hours since I've uploaded it. I even tried deleting and reuploading the changeset - still I get this error message above, and am not able de deploy.

Can anyone help with the cause or a solution to this problem?