t seems to solve the problem, but not in the way we should expect.
Microsoft is trying to kill FAT32, because it doesn't work very well. NTFS is far better (stolen from IBM's HPFS, but without the reliability built in, but they did add journaling). Unfortunately, we have only one reasonable option for file system compatibility, and that is FAT32. VISTA was the ultimate attempt to kill FAT32, and it will refuse to format a disk larger than 8GB (I think) as FAT32, for no good reason than described above. Win7 seems to have backed off on that, and it will format a 16GB disk as FAT32 (possibly even bigger). Windows can, apparently, work with a 512 GB FAT32 disk, if you can get it formatted that way, but I think that our FAT32 driver has trouble with large FAT32 partitions (more than about 32 GB). Using 30 GB is far more space than I would allocate (I use 15 GB on my 512 GB disk, and I actually use about 1GB of it).
The answer for OS/2 or eCS, is to use DFSEE to format the drive as FAT32. Windows, and OS/2, seem to be happy with that. Other (windows) tools might create the partition with an incompatible geometry, that OS/2 doesn't understand.
By the way, I make two suggestions about FAT32 in OS/2, or eCS. One is: Do not use the EA support. EAs are sort of nice, in a few cases, but they are far from necessary on data disks. You will find that you have far fewer compatibility problems if you turn that feature off. Second, I recommend REMing the cachef32.exe line in config.sys. FAT32 works faster, and more reliably without the cache, especially if you use it with USB devices.