If a file stop on the very same place, might be download corruption.
Do a CRC Check on them to see that you downloaded them correctly..
Usualy the animes comes with [Group]Name_extended_[XXXXXXX].avi/mp4/mkv
See the XXXX
thats the crc32 (search google there are a couple of programs that check thoses)
If the number that the program gives to you is different from the one that says in the filename, your download is corrupted.
Now that we got Download corruption out of the way, means that the file is ok, but still crashes on the same place.
You might have instaled CCCP, the codec pack, it comes with a pre-configured version of FFDSHOW.
THat might be putting a strain on your computer, thats why it "lags" on certain parts, or maybe even stop completely.
DBL-Click on the "FF video" icon, bellow, "Image Settings" there should be a bunch of options somes should be with a "check" on the right..
Just disable them all off, clicking on the box, to uncheck them.
Apply and ok..
You probably going to see a difference on the video itself, colors, blurring and such.. but see if that the mp4 hangs on the same place
"Chile is a thin and tall country"