Hmm, the above only works immediately after you found out the download speed reduced to zero. The problem is that when you launch the CMP the cache is emptied of all what you downloaded during the previous session. That is the reason to move the file out before restarting the CMP. The fact you can't find the file is probably because of that. Download the item again and if this happens again, going to zero and not installing, try what I described earlier.
Btw, under 5Mb file size for this problem to occur sounds a little bit iffy, maybe there's something wrong with the file, but it doesn't hurt to try again.
Greetings from nighttime Amsterdam,
Jan