When the arduino has an onboard cap in series from DTR pin to the chip's reset, then a cap is not needed on the CP2102 module.
Thanks for that - I'd been wondering why I'd seen the 0.1uF cap added to the board that RandallR pictured thinking that it shouldn't be needed if the 'arduino' has it's own 0.1uF cap on the reset line.
I guess the idea was to avoid having an extra cap on each clone you build? Too late for me, I always do that.
I'm posting just to confirm for the OP that I bought a pair of the same boards (or at least appear to be the same) that RandallR pictured from dealextreme and the "fix" was as simple as cutting the trace that goes to the RST pin and running a small wire from DTR. No 0.1uF cap needed if your target board already has it.
I also had to swap the TX/RX lines between the CP2102 and the target board (I've seen some boards where this wasn't needed).
Hope this helps,