We haven't seen this specific issue with MS Word, but some applications do not work correctly with standalone volumes, which can be seen as I/O errors or simply the inability to access a RAM disk.
To solve, try enabling the
HDD emulation option in the
RAM Disk settings. This option emulates a complete Hard Disk Drive with partitions indistinguishable from a real device, which usually fixes compatibility issues. The downside is that there is an extra layer of emulation that can reduce the RAM disk performance by 5-10%.