I have no problem setting my upload limit ( upload_max_filesize ) to 1 GB but for some reason 2 GB or above seems to be no go. Would anybody know why? Could it be one of the many 32-bit vs 64-bit issues?
upload_max_size is not the only variable that would affect uploading. You may also want to look at the settings for:
post_max_size -- uploading files is done through the HTTP POST mechanism so this has to be at least as big as upload_max_size memory_limit -- If memory limits are enabled, this also must be larger then upload_max_size
It may also be a 32bit limit as well:
(from php.net) Note: PHP allows shortcuts for bit values, including K (kilo), M (mega) and G (giga). PHP will do the conversions automatically if you use any of these. Be careful not to exceed the 32 bit signed integer limit (if you're using 32bit versions) as it will cause your script to fail.