i sent some money to my friend and didn't receive anything. In my transaction appear completed but on my friedn is nothing ! why ?
your friend is not on correct chain? - if so, he will/may still get the coins if he goes on the correct chain and you sent it to his "address", and you was on the correct chain.. (said my dowsing rods)
when did you send? what is tx id?
WE HAVE A SERIOUS PROBLEM HERE!
benysound2 just reported a missing transaction. I just tried a test transaction to Poloniex and it has also disappeared - it didn't show up on Poloniex, and nothing comes up in the block explorer:
Date: 19/03/2014 21:53
To: Poloniex HSWf3xsLaEQWjPnjCyVWnHCqAvfJaBHLxQ
Debit: -1.00 HUC
Net amount: -1.00 HUC
Transaction ID: 142545e13965eee1e1b631aecbd6cc53437ba858e2fdc8aef253cb0f72fb1d82
Even worse, here is a screenshot I took of my wallet on the block explorer the other day. As you can see, it lists 2 transactions on March the 13th (blocks 90032 and 90192):

Here are the details of those transactions as listed on Poloniex:
HUC 2311.91322849 HF55kSQJK2QtueW6DStM6FZem2gRBrpqSb 2014-03-13 20:09:00 COMPLETE: f8f574f3129b87ed0d8ed32b9b6a78d6db508283e536119667fe0a78f7bad9d7
HUC 2470.79067847 HF55kSQJK2QtueW6DStM6FZem2gRBrpqSb 2014-03-13 15:42:11 COMPLETE: 729b0b4742ed59592ca069abe9e04bbe15b0ee1a54dd71b332b1779aed2271ae
If you look at the block explorer now, you will see that those transactions have completely vanished:http://huc.explorer.dot-bit.org/a/HF55kSQJK2QtueW6DStM6FZem2gRBrpqSbI started from scratch and I was on the same chain as f2pool - everything appeared to be OK until today.
What has changed?
that top transaction went in.. it's in the chain
as for your other problem, looks like you withdraw in the fork window, they was on the wrong fork.. blockexplorer was also on the wrong fork ... (they froze market, but maybe never froze withdrawal?, or maybe you withdraw a couple of blocks before they froze...).
maybe those tx did not go out of poloneix and they have them back after they resynced, did you ask them to confirm the tx number (as not valid now)?
p.s. only thinking out loud atm