My last attempt at uploading a b&w film scan to Photobucket, totally washed away all the contrast:
Just incase anyone else has had the same issue, here is the response from Photobucket support:
This is a known issue affecting several users and our engineering team is troubleshooting the problem. We will get this resolved as soon as we can!
The original images are not affected, but the compression software for the web-size is not looking at the grey-scale correctly. We will be moving to another software for that over the next week or two.
Phil.