nm-applet crashes, network unstable

[Observer]

sysinfo: natty beta 2

nm-applet crashes with the following error info:

Message: Caught signal 15, shutting down...

[Observer (dbvweb)]

Further, wifi disconnect is very frequent with the latest kernel update.

My system is using rt61pci wifi module.

[Observer (dbvweb)]

lspci -vvnn

09:04.0 Network controller [0280]: Ralink corp. RT2561/RT61 rev B 802.11g [1814:0302]
 Subsystem: Device [18e8:6194]
 Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV+ VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
 Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=slow >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
 Latency: 64, Cache Line Size: 32 bytes
 Interrupt: pin A routed to IRQ 10
 Region 0: Memory at c0108000 (32-bit, non-prefetchable) [size=32K]
 Capabilities: [40] Power Management version 2
  Flags: PMEClk- DSI- D1- D2- AuxCurrent=0mA PME(D0-,D1-,D2-,D3hot-,D3cold-)
  Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
 Kernel driver in use: rt61pci
 Kernel modules: rt61pci

[Observer (dbvweb)]

wifi is extremely stable when I was using Jaunty. But with recent upgrade to natty, wifi connection is very unstable.