The "FIR" in its name stands for , which is the highest speed tier for IrDA technology.
Fluorescent lights (especially older tube lights) emit IR interference. Move to a dimly lit room or block ambient IR with a cardboard shield. Also, check for USB power saving: Go to Device Manager → USB Root Hub → Properties → Power Management → Uncheck "Allow the computer to turn off this device." U2IrDA Mini 4 MBPS FIR USB IrDA 20