AssetBundle incompatibility

I just started receiving the following error:

The asset bundle ‘http://***.unity3d’ couldn’t be loaded because it contains run-time classes of incompatible version. Rebuild the AssetBundle to fix this error.

I have tried rebuilding with the current version (3.5 RC1) and uploading to the server, but I seem to be stuck getting this message.
Anyone have any ideas why this is happening? I’ve posted to the beta group too, hopefully someone can help me find an answer.

More info:

I receive the following errors on Mesh Render and Particle Renderer of my asset:
AssetBundle loading failed because the MeshRenderer class serialization hash does not match. Supported: 2a66b79b, loading: 5ab6257e
AssetBundle loading failed because the ParticleRenderer class serialization hash does not match. Supported: e262cf75, loading: 92d7bacd

Update: I am not entirely sure the difference, but I deleted the original asset bundle from the server, increased the asset build number in LoadFromCacheOrDownload, and reuploaded. Seems to be working, tentatively.

Just a tip, I have a static build number, and I have recently incorporated a static asset build number, which I update when I upgrade my unity version, that way I can force re-download of the cache without going through the code to check my LoadFromCacheOrDownload calls.

For example:

WWW www = WWW.LoadFromCacheOrDownload (url, Changelog.AssetVersionNumber);

It happens when you changed scripts in the bundle. That is, you need to rebuild the bundle and upload again everytime you did changes to any asset in the bundle (include the scripts attached to the GameObjects)

A more detailed answer here.