Just to say, I just tried installing WordPress Importer again on a new install and this time it worked fine, so whatever the problem was seems to have been resolved.
@girish I think this can be marked as solved (it's too old for me to edit, turn into a question and mark solved myself).
@girish I have a 238 ko iCal file.
I've split it in twice and I went from 250 importation err from 1 err.
The problem should come from that, thanks!
I was at the beginning thinking about it (splitting the file) but after that, I was focusing on RateLimit - wrong way! Also, I advise people which want to import a big file to increase drastically the mem allowance of the app (2Gb in my case)
