your biggest concern will be the magnetic field generated by the ups, and the size of the field will depend on the size of your ups and whether it's just a line stabilizer w/battery back-up, or an actual line conditioner that passes the voltage through the batteries then converts it back to ac before routing to your ps. If it's just a stabilizer, it's not the ideal location but shouldn't impact any data storage on your hd. If it's a conditioner, the magnetic field will be larger and stronger, and could affect data on your hd, and I would suggest moving it.
if you think your ups doesn't generate a field, put it next to your monitor and watch what happens, but don't blame me :Q