I too have the same issue! I called htc and they first told me to 'reset to stock' my phone, then do the update at that time. I did that but still got the same thing each time (just like the first comment above). Then I called htc back and then they said the only way to get past this was to install a special sync software (only available for Windows not Macs) and then 'try' to install a different custom rom that was ment for a different device, because they said they did not have access to the Sensation Rom. WOW, HTC's customer support is the worst ever, it's like they didn't even know where to start and they were making it up as they went. by the way, that last suggestion they mentioned about the different rom, didn't work either.
If anyone out there has found a way around this, please post the solution here, I and many others will be very grateful!