problem loading u-boot over UART using ldr in Windows

I am trying to load u-boot over UART using bfin-uclinux-ldr, however it keeps freezing up during the "Sending" phase:

Loading LDR u-boot-bf537-stamp-uart-2010R1-RC2.ldr ... OK!
Opening /COM1... OK!
Configuring terminal I/O ... OK!
Trying to send autobaud ... OK!
Trying to read autobaud ... OK!
Checking autobaud ... OK!
Autobaud result: 115200bps 49.766mhz (header:0xBF DLL:0x1B DLH:0x00 fin:0x00)
Sending blocks of DXE 1 ... [1

It has worked in the past, but has recently stopped.

How can I fix this?