Computation Error on AMD/ATI Radeon GPU with OpenCL and Windows OS

<message>
Network access is denied.
(0x41) - exit code 65 (0x41)</message>

This is spurious. The science app produces an exit code that would be meaningful to the author of that code.  However Windows sees that code and interprets it as a Windows error - which it is not - so the text is just wrong.           

% Opening inputfile: ../../projects/einsteinathome.org/LATeah0055L.dat
% Total amount of photon times: 30007
% Preparing toplist of length: 10
% Read 1255 binary points
read_checkpoint(): Couldn't open file 'LATeah0055L_980.0_0_0.0_8218995_1_0.out.cpt': No such file or directory (2)
% fft_size: 16777216 (0x1000000); alloc: 67108872
% Sky point 1/1
% Binary point 1/1255
% Creating FFT plan.
% fft length: 16777216 (0x1000000)
% Scratch buffer size: 136314880
% Starting semicoherent search over f0 and f1.
% nf1dots: 31 df1dot: 3.344368011e-015 f1dot_start: -1e-013 f1dot_band: 1e-013
% Filling array of photon pairs

In the above snip, everything is normal for the start of crunching.  A checkpoint file (.cpt extension) will only exist if this task is being restarted from a saved checkpoint.  The read_checkpoint() function looks for a checkpoint that would have been saved if there had been some crunching of this task previously.  No checkpoint was found so crunching is starting right at the beginning at Binary point #1 out of a total of 1255 to be done.

The problem then arises pretty much immediately.                  

Error in computing index of fft input array, i:1055167508 pair:13768
ERROR: prepare_ts_2_phase_diff_sorted() returned with error 2288728
00:52:46 (2724): [CRITICAL]: ERROR: MAIN() returned with error '1'

The above will be meaningful to the author of the science app.  Hopefully, one of the staff might find time to have a quick look and comment about why this might be happening.  It seems unlikely that this is a program bug as millions of these tasks have already been crunched successfully.  You would expect many similar reports if it were a bug.  That really leaves two possibilities.   

It could be a hardware issue with your graphics card.  Seeing as you have two identical systems, you could swap graphics cards and see if the problem goes with the card or stays with the system.  If it stays with the system, it's not the card - it's hardly likely that two different cards would have the same hardware error.

If it's not the card, the second possibility is the OS/driver combination.  As the 'Northern Islands' cards are getting a bit old now, there could be something in recent drivers that is not quite compatible.  It would be useful to see if there is any difference in behaviour with an earlier driver.  I'd be tempted to try to find a version around the 2015 to early 2016 mark.  From what other people have reported, it's pretty important to clean all the remnants of a previous driver install when updating or downgrading a driver. Maybe the very first step should just be a complete clean and reinstall of the current driver to see if that makes any difference.

You can't always assume that because it works on one project it will work on all others.  You also can't assume that because one card doesn't work, a similar card in a different machine also won't work.  Did you actually give your 'seti machine' the chance to see if it could handle an Einstein GPU task?