Win500 now works, culprit was Data Execution Prevention
The culprit on my 32 bit Vista machine was Data Execution Prevention, which is set to OptOut by default. Once I added Win500 to the OptOut list, Win500 1.88 came up immediately and ran fine (including interfacing with the RR web service).
To opt a program out of Data Execution Prevention, go to Control Panel->System->Advanced System Settings. Click the Settings button under Performance, then click on the Data Execution Prevention tab.
You have a choice of turning on DEP only for essential Windows programs and services or turning on DEP for all programs except those you select (this was the default setting on my system). Once I added Win500 to the exception list, the crashes went away.