ReflexTestEnabled.exe returns "ERROR: _SaveSettings -1."

[simco50]

Trying to run ReflexTestEnable.exe 1 fails immediately with this message:

\utils\reflex>ReflexTestEnable.exe 1

ERROR: _SaveSettings -1.

Running the test afterwards result in the following:

Searching for  90.0 FPS...
    Trying   4000000 kHz... GPCCLK = 2730, DRAMCLK = 11201, Util = 98.0, FPS =  93.8, PC Latency =  85.774
    Trying   2620637 kHz... GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.0, PC Latency =  94.662
Measuring:    Reflex ON,  Frame Gen x2...
                            GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.3, PC Latency =  90.525
                            GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.4, PC Latency =  87.277
                            GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.2, PC Latency =  80.625
                            GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.2, PC Latency =  88.481
                            GPCCLK = 2625, DRAMCLK = 11201, Util = 99.0, FPS =  91.3, PC Latency =  92.447
Measuring:   Reflex OFF,  Frame Gen x2...

ERROR: Failed to override Reflex.

What is going wrong here? And could these messages be more descriptive?