Heh, a blast from the past
The patching process could be a bit more sensible, it depends on what version you have bought and so on.
I've used
ArmA website so at least some of those sets should work, just pick the right "category" for the version of the game you have bought.
Also you have to re-install the whole game from scratch when the patch installer fails because it has corrupted the pbo file it halts on and subsequent patching tries will halt there as well because the file is corrupt.
Other than that, don't really know why that would happen, don't remember having much problems with the patching myself..