array_multisort ... unsupported in different builds?

ok, heres the thing short version; array_multisort works on localhost but when i upload it, ceases to work (array is left unsorted) long version; i have array_multisort sorting a multi dimensional array with sort_asc. i understand that it sorts by the first index by default. on my localhost (iis on xp, php4.3.3) it works perfectly sorting the whole array based on the first row, but when i upload the code to the online webserver the array_multisort does nothing. no sorting is taking place, its as though the line is being skipped, but its not in the middle of an if statement or any other possible means of being skipped logically. ive tried uploading this on a both a 4.3.3 server and a 4.3.2 with the same result. i started off with just listing the parts of the array, eg array(something, something else, blah) so it assigns index numbers. then as part of updating various things i changed that to set the indexes myself, eg array(indexname => something, index2 =>somethingelse) etc. it was working online before so ive tried putting just the first row as non-assigned index, and going back to number indexes for the whole lot, and no dice. can anyone suggest why this would work fine on my machine and yet cease to function on another server of the same version? im completely at a loss and p***ed off. tia john