NiSlo,
If you did not execute an ATWCS command after changing to the new baud rates you should be able to simply power down and power back up, but the fact that you can see the LED's display the new baud rate leads me to believe that you wre able to connect at 115200 and then issue the ATWCS command, so I would redo the hyperterm settings and try again. The settings should be No parity, 8 databits, 1 stop bit and like lukeyson mentioned flow control should be set to none.
Thanks
Paul
www.obdpros.com