Truble whith lo speed wi-fi connection

I am installed open SuSe 11.0 at notebook Benq R22E with wi-fi RT2500.
Access point use 128-bit WEP encryption.
I did not check the speed of wi-fi connection without encryption.

Now I have a connection speed allows use 1024 kbit/s for download but maximum speed for download near 240 kbit/s.

In Windows I have the normal speed for the connection.