First thing to do is turn off the GPU option on the performance tab of the LR Preferences.
This option is already turned off.
Most calibration software offers an advanced setting, so if it gives you a choice, go for a brightness of around 100-120 cd/m2, 6500K or native white point for an LCD monitor, and most importantly, an ICC2 Matrix profile rather than an ICC4 or LUT-based profile, as these more recent profiles aren’t compatible with many programs yet.
You'll have to dig into the calibrator's software to figure out how to configure that.
I re-calibrated the monitor using the ICC version 2 settings under preferences and everything changed back. Lightroom must not support the version 4 profiles.
Thanks for your help.
Lightroom must not support the version 4 profiles.
It's not as simple as that. I've tested v4 in Lightroom without seeing any problems.
But some calibration software fails to follow strict specifications when writing profiles. This seems to happen more frequently with v4 than with v2, probably because the v2 spec is simpler and/or better established.
The same thing goes for matrix vs. table-based profiles. The latter are much more complex (although supposedly more accurate), so the potential for errors is higher.
It all comes down to the software writing the profiles. If it's not done done correctly, Lightroom chokes very easily.