For those of you wondering what is the problem with Riesel Sieve, here is a word from BOINC side administrator Bryan:
Basically, the project creator has disappeared. People have been in contact with him, but we haven't heard any resumption date or even if things will resume. For the time being, I'm focusing my efforts on getting the non-BOINC side of the project up, as it is far easier and requires far less resources. We do not have access to any of the databases or we would have been able to restore things even without the project creator.
Our wishes for RS to return as soon as possible.

Comments on the following newsitem http://www.primegrid.com//all_news.php#74

Finally, some info.