Just completed a conversion of 50,000 SPG points to MR points. I did this at the SPG website and was surprised to see that you can go both ways at the SPG site. When I had problems with the process I checked the Marriott site to see if I could do it from Marriott. Apparently it is only at the SPG site. When I clicked on the "convert points" tab at the SPG site it popped up a window with a field to enter the SPG point amount you wanted to convert and a second field that would indicate the amount of MR points you would get. My first try I entered 50,000 and I got an error message saying I had to enter only 1,000 point increments. I entered 50 and got the same message. I called SPG and spoke with a very helpful woman and I asked if there were any know issues with the conversion process? She said that she was not aware of any and admitted she had just come on duty, went off to check if there was a problem. No known problem, suggested I log out and re-log in, stayed on the line while I did that, to no effect. Went and talked with somebody else. She tried to look at other web locations. Finally asked that I enter 50,000 again, 50 again and finally 50000. The 50000 worked! Within a minute I had an e-mail from SPG noting the transfer had been completed. Not showing up on my Marriott account after 35 minutes, but I am not in a hurry.