Looks like Apple closed the firmware window on 5.0.1 this evening at about 22:00 GMT. According to my tests, new SHSH Blobs for 5.0.1 are no longer being provided.
See our FAQ here for more detail - http://www.iphoneforums.net/forum/i.../shsh-blobs-frequently-asked-questions-19986/
See our FAQ here for more detail - http://www.iphoneforums.net/forum/i.../shsh-blobs-frequently-asked-questions-19986/