Montreal, I've been Marriott for years & not once have I ever been told no for a Marriott reward. On the contrary, I've found them to be easier to redeem than other programs. But - to your question. The weekend you've chosen to visit Chicago is also a holiday weekend in America, so perhaps that's impacting their inventory. I would try calling the hotel directly.
Also, in Cat 4, there is the Courtyard by Marriott downtown; you might check there. And not optimal but doable is Chicago Marriott O'Hare, which is next to the El station that takes you downtown.
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Sharon
[This message has been edited by SkiAdcock (edited 04-15-2003).]