Unknown floating point exception e881

[aas333]

I am running a sytem in ApSim, about 1/3 of the way through the simulation (April 2nd) the simulation stops and I get an error readout of:

Unknown floating point exception e881
Floating point co-processor fault at address 0042b2e8
0042b0b0 COOLER SIM [+0238]
00429bf0 COOLER_MOD!COOLER [+0b09]
004c13c0 SIMUL2B [+0321]
004cd560 SSCALC [+0c8c]
0040c500 ANAPS [+0640]
004beca0 SIM [+0127]
0041a860 CALCS [+03b9]
004875b9 CALCSZ [+0060]

Does anyone know what piece of equipment cooler is, what might be causing this error, or how I might go about troubleshooting it?

Thanks in advance for any help!