More often than not, Apple will temporarily disable your Apple ID when they detect unusual activity on your account. This may result from an unusual number (or dollar amount) of purchases, of if Apple detects that you are signing in from a location which is abnormal.
Are you able to sign in via iTunes on your computer -- just not your mobile device(s)? If so, you may be able to resolve the problem on your mobile device(s) by signing out of iCloud and then signing back in again. This would force an account refresh on your device and you'd be back in business.
If you cannot sign in on any device, you may need to contact Apple directly in regard to the issue: http://www.apple.com/support/itunes/contact/
If we can be of any further assistance, please let us know!
Hello again! It's been awhile since we chatted, and I wanted to follow up and make sure that the solution I provided worked for you? When you have the chance, would you kindly let me know?
Thanks so much, and I look forward to hearing back from you!