For me the Wifi-Connection timed out very often. The mentioned solution to stabilized the connection with iwconfig doesn't solved the problem. So I switched to ndiswrapper using the Win98-Driver from this site: http://www.realtek.com.tw/downloads/downloadsView.aspx?Langid=1&PFid=1&Level=6&Conn=5&DownTypeID=3&GetDown=false&Downloads=true
This solved the problem for me. Maybe it should be mentioned on the page.
EDIT: This version of the driver freezed the kernel some minutes after using it. This version seems to be ok: http://www.majorgeeks.com/Realtek_RTL8187_USB_Wireless_LAN_ME2000XP_d5165.html (v1221)