Error message.

[nogueira13 <nogueira13 gmail com>]

I am having some problem when I try to use a wireless network that is in a building near my home. The signal level is not too strong, but, when I boot by windows 7 (I have dual boot in my Laptop) despite the weakness of the signal I have a very stable connection. But when I boot by Ubuntu 10.04 64 bits, in the same position at home, I get a connection very unstable, with the connection dropping at 2 minutes or less. I debug  it in my syslog and I would like to show the output to see if you may help me with this problem. The output is in the link:

http://pastebin.com/GBvWndXN

I don't know what does mean: "Aug 17 17:12:28 nogueira-dell kernel: [  774.973853] wlan0: disassociated from 00:21:8d:21:0e:51 (Reason: 14)"

What does mean Reason 14?

Well, I beg your perdon for my poor English, but my Native Language is the Brasilian Portuguese. Thanks in advance for any help.
Antonio Carlos