I've recently had the same problem but it does seem to vary depending on the hotel as many corporate stays of mine posted OK.

Looking at the page they referred me to (which I guess is the same one) it said something about in the US points may be collected at conference, meeting and locally negotiated rates if these rates are discounted less than 30%. I couldn't see anything which specifically mentioned not getting points at corporate discounts greater than that 30%.

However I didn't feel like pushing it as it was only one night and it was a cheap rate so I wouldn't have got many points anyway. Your loss is much greater!