Lpc2000

I have samples of LPC2138 and I built a prototype board.
With an evaluation version of CrossStudio I created a simple blinking 
LEDs application.
Using Philips flash utility I am able to program the micro and it 
works. Have problems however with debugging and programming through 
JTAG. I tried both JLink and Olimex wiggler compatible jtags, which 
are working fine with another board (IAR Kicstart Kit for LPC2106)
using either IAR or RA software.
With 2138 board I am able to connect to JTAG (from CrossStudio menu),
but when trying to do anything else, JTAG is loosing communication 
with the target.
My JTAG interface hardware is a copy of the one used on the Keil 
MCB2130 evaluation board (see schematic here
http://www.keil.com/mcb2130/mcb2130-schematics.pdf )
I checked the connections and all looks OK. 
The supply voltage (+3.3V) is very clean and connections between 
microcontroller and JTAG socket are rather short.
Any hints or suggestions will be appreciated.

Jan.