Here's more about the cables I'd like to use with Ubuntu:

Kosmos USB-COM-Adapter, Art Nr 703 921 contains a Sipex SP232EEP DIP
IC and a second IC on the board under a blob of black plastic. This
came with a Thames and Kosmos Toys kit with an Atmel ATTINY2313-20SU
microcontroller. With the Thames and Kosmos application loaded under
Vista this cable works. It does not work with the other
applications.

Radio Shack USB Special Cable, color white with no other markings. I
can not open the molded circuit box without destroying it. I bought
it to use with the BASIC Stamp microcontroller learning kit Radio
Shack sells. Does not work with Radio Shack's BASIC Stamp
application loaded under Vista. When the application is loaded on my
Lenovo laptop (when it had Vista on it), connecting the battery to
the BASIC Stamp board kicked the Lenovo into Visa's white screen of
death mode.

I though I had tried a third cable. But it was something else—USB to
propriatory protocol.

Now that you got me to take a closer look at these cables I realize I
should get a general-purpose USB-to-RS232 adapter cable with a
recommended chip set.