It is 9:57 a.m. (GMT-5) here in Massachusetts on Friday, 2015-Dec-11 and I have multiple times experiernced this as well: "the update has been checked and is corrupt". It is not working for me, either by the auto-check for updates or by my manually checking for updates. In fact, after the first error message I manually checked for an update and was told my "Xara Designer Pro X 11.2.4.41531 DL x64 Nov 4 2015" version is up to date!!

At this point, I don't trust an update declaring itself as being corrupt and will hold off for now.