Digital BW, The Print

I'm using qtr on a PC with an Epson 2100. I'm using qtrgui. Current
versions of each.

I've been working with a test image. Saved as a grayscale .tiff [-
with embedded profile = Gray Gamma 2.2 -- also tried using Dot Grain
20% though I'm guessing that this isn't the issue.].

Works fine and produces a nicely neutral print. I'm already impressed
with the result. I'm using Epson Archival Matte (Enhanced Matte) with
the Matte Black cartridge. Paper type set to 'Matte'.

However (I wanted to experiment making a slightly warmer print) - any
combination of the curves settings (other than none) seems to cause
Windows to give me a printing error: "quadtoprinter.exe has
encountered a problem and needs to close." Etc. Though the program
doesn't actually shutdown.

For example - when trying to use UC-EEnhMAtte-warm &
UC-EEnhMAtte-cool. I'm assuming that the UC stands for Ultrachrome.
I'm using Ultrachrome inks.

Any help would be very much appreciated. I searched the messages over
the past couple of days. Apologies if I've missed something obvious
and this has been raised previously.