Bruno - I think you may have been affected by the problems they were having a while ago. Have you attempted to read their newsletters? I tried once, and they talked about having serious problems for a while, but have since moved to a new facility, and have scaled back on the amount of space/bandwidth that they offer.

*edit*
I found a description of what their problems were:
http://blog.dreamhost.com/2006/09/19/anatomy-of-a-disaster-part-2/