  The Ultraviolet Coronagraph Spectrometer (UVCS) aboard the {\it SOHO}
satellite has observed very fast Coronal Mass Ejections (CMEs) associated with
X-class flares. These events show spectral signatures different than those seen
in most other CMEs in terms of very rapid disruption of the pre-CME streamer,
very high Doppler shifts and high temperature plasma visible in the [Fe XVIII]
emission line. This paper describes three very similar events on 21 April, 23
July and 24 August 2002 associated with X-class flares. We determine the
physical parameters of the pre-CME streamers and discuss the geometrical and
physical nature of the streamer blowouts. In the 21 April event, the hot plasma
seen as [Fe XVIII] is not related to the structure seen in [Fe XXI] by SUMER at
lower heights. It has the form of a rapidly expanding fan, quite likely a
current sheet. In the August event, on the other hand, the [Fe XVIII] is
probably a bubble of hot plasma formed by reconnection in the wake of the CME.
C III emission from the July 23 flare is detected as stray light in the UVCS
aperture. It precedes the hard X-ray brightening by about 2 minutes.
