This seems to be a problem with the software program that you are using. I just downloaded it with PSREdit 500, and everything went just fine. There seems to be an software bug with Win500 and Phase-II P25 trunking systems. You might want to contact their technical support for further advice.
"A bank is a place where they lend you an umbrella in fair weather and ask for it back when it begins to rain." Robert Frost.