I downloaded the 'clean x-10' basic set-up from the files here and all the controls work perfectly with the exception of the 'all off.' Sometimes it works just fine, other times it requires sevel taps on the button, and sometimes it doesn't work at all. Any ideas or suggestions? Thanks in advance......

Try pushing the 'all off' button on the IR543 a number of times to see if it works reliably or if you have similar problems.

If the button on the IR543 works reliably then you have an IR problem.

If the button on the IR543 has the same problem then you have a noise and/or phase coupling problem.

I found that my laptop was generating enough RF noise to create major problems with the X10 when it was plugged in and I sent a “dim” or “all off” command. The way I tracked the problem to the source was to unplug different things around the house one at a time. After I would unplug something, I'd push "all off". Finally the culprit revealed itself to be the laptop when it was plugged into the power line whether it was on or off.
I found some adapters on www.smarthome.com that totally absorb the excess noise and now the system runs fine when the laptop is plugged in. The location of the part at Smarthome is:
[Link: smarthome.com]
Give it a try, unplug your electronics one at a time, (even try the refrigerator!) If you find the source add a Leviton noise filter. If that still does not do the trick, look into "phase bridges"... Some houses are wired wrong and the X10 only crosses over the lights on the 110V side they are plugged into. There is a product out there that you can use to bridge to any 220V plug on your dryer or oven with another part from Smarthome. That web address is:
[Link: smarthome.com]
Good luck!

The X10Pro plug-in 5A filter is $17.35 and the 15A filter is $48.10 at [Link: homeautomationnet.com] vs. $26.95 and $64.99 at Smarthome.