I update the ACID tables daily and the entry for the ixus310 101a should result in a proper download. I note that ACID tried to download build 2033 but the current build is now 2044. I suspect that the trunk code page was updated while you were running ACID so when it first went to the trunk page (to get the list of builds) it said 2033 but when sometime later you clicked the download button the page had been updated to a later build.
I'll see if I can catch this sort of error somehow.