It could have been a bad download. I did download it twice and try it twice.
Hard saying. Maybe just one of those things.
It can very easily be a bad download twice. Slow internet speed and server errors are the main culprits. That is why you always need to check the md5 sum of the download against the provided md5 sum. If they don't match, the download is corrupt.
With ICS and Jellybean ROMs Ram is usually low to begin with. To combat this use Fast Reboot. It safely closes all apps, then opens only those that need to be running by design.
Clean all caches every day.
Most ICS and Jellybean ROMs require that you have a 1.0GB-1.5GB partition on the SD card. Usually in the ext.4 format.
Rule of thumb: You cannot use more than 20% of the actual space available on the SD card or 2GB (Which ever comes first), for the partition.
Easiest way to partition sd card is with recovery (Formats to ext.3), then reformat that partition to ext.4 with Mini Tool Partition Wizard- Home edition.
Link2SD gives you more app movement and deletion control than any other, as well as converting system app to user app + user app to system app. Thats total control of all downloaded and pre-installed system apps.
The best Jellybean ROM is the SlimRom by thekraven. I have a slight mod/theme of this ROM (Bean_Whiz-CM10).
ICS has some security problems.
The best Gingerbread ROM is the MiRaGe. I have flashed it numerous times on both V's with the ZenGarden recovery.
The best Recovery for the V is the BobZohme modified ClockworkMod (VM670NH) recovery. It can flash absolutely anything. It doesn't have the "fix recovery loop" option so you need to keep the zipped version of the Xionia recovery (ZV4 V) or the zipped version of the COT (ZV5 V) on the root of the sd card just in case.
If a ROM doesn't boot it is caused by one of the following:
Corrupt download
Recovery inadequate
SD partition is the wrong format for the ROM.
Full wipe and format not done properly
Flashing kernel or patch in the wrong order (always Flash: ROM, kernel or fix/patch, Gapps.
All CM7-CM10 ROMs developed for our V will boot up on every V. If not then one of the above problems is at fault, not the actual ROM.