Support for the Realtek RTL8187B chipset is still experimental and is not 100% functional.
Recent kernels (2.6.27 and newer) contain a fully-functional driver for RTL8187B - it's the same driver as the new one for RTL8187L, rtl8187. You should consider trying that version. The new driver is mac80211-based, so the usual mac80211 rules apply. This driver is included in the BackTrack 4 beta release. Also see: http://forum.aircrack-ng.org/index.php?topic=5297.msg28847#msg28847.