Despite Mass Effect 3's impressive mastery of the atmosphere, it still can't quite handle clouds. EA is "aware of an issue" that prevents Mass Effect 2 save files that either exist in the cloud, or were transferred to a new 360 through the cloud, from being imported into ME3.
EA's help guide for the problem makes no mention of plans to implement such functionality, but it does offer solutions, provided you still have access to the 360 that birthed your ME2 save. If your ME2 save exists in the cloud and you're playing from its original console, simply move it back to your hard drive and it should import fine.
If it exists on a new console and was transferred through the cloud, it'll need to be moved back to its original 360, and then re-transferred to the new system using a memory card or USB thumb drive. If you no longer have access to that original 360, it looks like you're going to be spending some time on the character creation screen. But hey, don't feel guilty, all right? Shepard would have wanted you to love again.