0841 keeps reading packets

[ccars111]

hi ive cracked quite a few wep keys in my time i have a alfa AWUS036H, when a client is on the network and there is even 5 data packets i can crack it in minutes, when the are no clients ad no data i can still crack it using the 0841 attack, but to my disapoitment there have been two clients i can not crack, when i use the 3000 attack to keep alive packet, i then run the 0841 and all it does is read packets continosly, i got up to 10000 and still no use this packet came up, i had 55-60 pwr and i just do not understand it , is there anything else i could try? its happend on a couple of occasions but i have done it this way and has worked on some routers thanks

any help guys