only 10meters Range

hello there

i’ve got 2 XBees Series 1 with flat antenna up an running. they are on theyr own PAN and working correct. After 8-10 meters i loose connection. I put them both on a usb explorer board and mad the range test with the digi software. same result, but still 85% signal strengt after loosing contact…
The Xmit power is on highest.

what could be wrong ?