QTR-Quadtone RIP

I am evaluating QTR and so far am very happy but have some strange 
behaviour that I haven't been able to figure out.

Basically if I print to file out of Qimage using an image size under 
a certain threshold QTR happily agrees to print the file. If the 
image size exceeds the threshold QTR complains of 'Invalid TIFF Tags 
in image' and 'TIFF format not supported'

My workflow is:

In PS CS2
Photoediting as a monochromatic RGB in QTR-RGB-Gray workspace
Resize image (without interpolation) and save as tiff  (with profile 
embedded). Note that I do the resize in PS simply to take note of the 
image dimensions.

In Qimage
Choose Print to File and assign exact dimensions of image as 
previously noted as paper size. Set resolution to 720 ppi.
Under Custom button in printing pane, select specify size and enter 
same size coordinates.
In Color Management settings enable Printer Profiles and select QTR-
RGB-Gray Matte Paper.

In QTR
Basic set up for Super A3 paper size (13x19 on the dropdown), curves 
etc…
Select Image from File Menu. This is where the wheels fall off.

I haven't determined exactly where the threshold is but if I print to 
file out of Qimage with an image size of 36 cm wide QTR shows me the 
thumbnail in the print pane and appears happy to print. If I work 
with 46 cm wide (which is what I want to do) I get the above 
noted  'Invalid TIFF Tags in image' and 'TIFF format not supported' 
warnings. 

Up until now I have been proofing with A4 EEM and everything has been 
fine as I have been working at image widths of 28 cm. The reason I am 
at 46 cm is I now want to make a print on Super A3 stock. I've not 
tried to print because I don't want to waste good paper given the 
error warnings.

Instead I have tried all sorts of combinations of the workflow 
including remaining with ProPhoto RGB in PS CS2 and not using any 
printer profile out of Qimage. I have uninstalled and reinstalled 
both QTR and Qimage (including using QTR cleanout), have backtracked 
from QTR 2.3 to 2.2f, and have installed the latest update of Qimage.
 
Nothing seems to work. A 46 cm wide image, as interpolated to 720 ppi 
by Qimage (from an 8 megapixel original) doesn't seem to fly in QTR. 
If I simply resize in PS CS2 to 46 cm wide and do not interpolate (so 
the resolution drops to 140 ppi or something like that), the file is 
happily brought into QTR. That seems the only way so far that I can 
get QTR to be ready to print a larger image like this, but I don't 
want to drop the resolution like this and forego the interpolation 
and smart sharpening capabilities of Qimage.

I have tried doing a lot of searches yesterday to come up with an 
explanation for this. I did see some posts on the Qimage list about a 
memory threshold problem, but that threshold was at a number of 
pixels that would far exceed what this image at 46 cm wide would have 
(which would be 13,039 in the longest dimension). I also read a good 
deal of exchange about the QTR-RGB and QTR-Gray profiles and their 
use in general and under Qimage and did note some remarks there about 
errors that could be generated, but I note this behaviour even 
without those profiles being used.

So I am stumped. Does anyone have an idea on how I can get Qimage and 
QTR working together to give me 720 ppi prints that make full use of 
the Super A3 capabilities of my Epson 2100?

Thanks for any insights,

Dave Meddings