DO NOT USE THE DRIVER CD from the USB-RS232 adapter box. (only as a last chance after you tried everything else without luck, but that should never happen). The driver from the adapter-cable CD is likely to cause you many problems.
Instead, download
- [Prolific Windows driver (2009-01-14)], which contains the 2.0.5.111 XP driver, that seems to behave. We investigated several cases, where this cured the communication problems.
Most of the WINDOWS drivers released by prolific over the years were seriously broken. What's worse, they seemed to work with TerminalProgram, and under some circumstances (not sending too much data at a time, waiting a lot, etc...).
Prolific windows-XP driver version 2.0.2.1 (2005-07-25) is broken without any doubt.. Verify in the device manager / com ports / properties that you do not have this.
- other drivers from 2003 also suspected to be broken (reports from non-developers).
- 2.0.0.26 (2004-06-25) seems to work on at least one windows-XP, but not recommended anyway
- (2007-xx-xx_ seemed to work on at least one windows-XP, but not recommended anyway
The broken 2003-2005 drivers are more common than one would think, included on many CD's even several years after prolific found out it's broken and fixed in new releases. Somehow the information did not make it to the 10 cable manufacturers prolific sells millions of these (HW-wise great!) chips. Maybe it's a good idea to notify manufacturers who purchase millions of these chips with broken drivers released. That way they would learn about the situation and the need to upgrade driver (it takes 3 minutes for an enduser to upgrade after 500 mins of headache caused by apparently application problems, and maybe 0.01 min / sold cable for the manufacturer to update the zipfile on the CD). Unfortunately the notification either didn't happen, or was unsuccessful.
- we contacted prolific about the PL2303 driver when we were only 99% sure that the XP driver was broken, but we never received a reply. Now that we met more cases, made more investigations and know for 100%, fortunately prolific has a newer driver for download that works so much better.
Your driver might be broken even if it works for some applications, or work "sometimes". In many cases it appeared that VemsTune communication was bad when in fact the prolific windows driver lost data and reported bad about the buffers.
Sorry about the inconvenience. If you use the recommended driver, and still have communication problems, make sure to report windows and driver version as well. Only saying that "the cable works with ... app and not with ... is not enough information".