>Is the property value stored correctly in the SCX/VCX?

It is not stored. Assigned in code.

>>A combo's rowsourcetype=1, columncount=2, and the rowsource is built as a long string, like this:
>>
>>.rowsource="first string,1,second string,2,third string,3, ... tenth string,10"
>>
>>The controlsource is actually a character (but may be a numeric - and I didn't try to see what happens then). Now comes the weird part: when the length of rowsource string exceeds 255, the last entry before the boundary matches a blank value.
>>
>>I think it's because it's missing its pair, the value for the 2nd column, which is by default "". Since it's the last one, it's matched if nothing else matches.
>>
>>This is not a problem to fix - IMO, the hard part was to catch it and understand how it happens. I do hope to go down in history as the guy who found the LAST combo's bug :) (IOW - it'd be so nice if there weren't any more).