I think at this stage its safe to say SEGA has no intention of providing any further support on this issue. I myself have opened several tickets but they either deny the issue, play it down to a cache/save data issue or claim its already fixed.
So we've tried putting our hopes on SEGA and it hasn't worked. I say its now time to turn to the gaming community. XBLA games are essentially shareware. Handing out copies just gives your friends who don't already own it access to a trial of the game. And as the trial version is freely available, handing out copies of it isn't illegial.
So my suggestion is for someone who has the 1.5gb version to copy the game onto an empty xbox formatted USB stick. Then upload the files on this stick somewhere on the net. The rest of us would copy these files, place them on an empty USB and then plug that USB into our xbox and over-writed the crappy 1.6gb version with the 1.5gb version.
Obviously this solution requires someone from the gaming community with the correct version of the game to step up for us. So lets see if the community is more supportive than SEGA is.