I cannot see any squares or lines here but I am using linux not Windows. You have poor vision ? What application are you using to view your jpegs.
The image posted does not look like it comes from Gimp. Using the ImageMagick identify utility I see a resolution (ppi) of 1x1 and I have never seen that before. Even if I set the ppi to 1x1 in Gimp I do not get that entry. I would expect Gimp to open that image "355-blah-de-blah-51_n.jpg" and impose a default ppi typically 72 or 96 prior to Exporting. In any case you can set a ppi using Image -> Print Size
It might be a hardware issue. Can you give some computer specs + which version of Gimp (find it in Help -> About). The more information the better.
The image posted does not look like it comes from Gimp. Using the ImageMagick identify utility I see a resolution (ppi) of 1x1 and I have never seen that before. Even if I set the ppi to 1x1 in Gimp I do not get that entry. I would expect Gimp to open that image "355-blah-de-blah-51_n.jpg" and impose a default ppi typically 72 or 96 prior to Exporting. In any case you can set a ppi using Image -> Print Size
It might be a hardware issue. Can you give some computer specs + which version of Gimp (find it in Help -> About). The more information the better.