Flash programming with J-Link Pro and J-Flash using the ethernet interface fails at JTAG speeds > 500kHz. The programming stops with either erase, program or verify errors but the exact point is not predictable. For example:

- ERROR: Verification failed @ address 0x1000BFEE (Read: 0x07, Expected: 0x00)
- ERROR: Failed to verify target

Flash programming using the USB interface is possible without any errors even at JTAG speed 12000kHz. Any ideas?

Versions:
J-Flash ARM V4.12
SEGGER J-Link Commander V4.12
Compiled Feb 26 2010 19:23:14
DLL version V4.12, compiled Feb 26 2010 19:22:53
Firmware: J-Link ARM-Pro V3.x compiled Dec 1 2009 11:36:38
Hardware: V3.00