seams with textures made in gimpshop

I have a 1536 x 512 image that i have cut into 3 512 x 512 tga files using gimpshop.
I have downloaded them to SL,
but when i put them on ajoining prims i get a seam at the joints.
if I zoom in very close there seems to be a shadow at the edge of each texture.
if i look at the originals in gimpshop i can't see this shadow.

does anyone know why this is happening and how to cure it ?

The prims are aligned and the other faces all have a transparent texture,
and have transparency set to max.

Thanks

Maybe when you used the select tool you may have had 'feather' on. Try setting that to zero.

no - feather is off

I had that problem. It's because the line you used to cut doesn't overlap. I had the same problem and yes, I used the ruler on the side to make sure I cut each piece clean. I didn't finish that project so all I have for you are ideas.

Use the smudge finger very lightly at the top and bottom of the ajoining pictures.
Work on Kornscopes idea. There is probably some type of feathering.
Make each cut a little lower and higher than you think they should be and adjust the texture on the item after you place it so the line goes up or down and is out of sight.

Most likely, the problem is not anything you're doing wrong in GIMP; it's all SL. Because SL does not clamp textures (it tries to tile everything), it's very common that an edge of a prim face will show a line of pixels from the opposite edge. This is most often visible when you've got a texture that is opaque on one end, and transparent on the other (you end up seeing a thin line on the edge of the transparent part), but it also tends to show when you're trying to slice images in the manner you described.

The solution is not to pre-slice in GIMP, and to let SL handle it internally via the texture repeat and offset settings. Now, obviously, you can't upload a 1536x512 wide texture to SL successfuly; it'll get shrunk disproportionately to 1024x512. What I would suggest is to shrink it yourself first in GIMP by 50% to 768x256. GIMP will do a nicer job on the resampling than will the SL uploader, and the ratio of 50% will yield the cleanest possible results. Then simply mount the image on a 1024x256 canvas, and upload it. From there, it's just a question of setting the repeats and offsets within SL to display just the part of the image you want on each prim. The end result should look totally seamless.

Whenever the repeats per face are less than one, the tiling/clamping thing becomes a non issue.

Thanks for your help people.
Chosen Few your sugestion solved it compleatly. For most of the things i'm doing a simplified version of just setting repeats to just less than 1 is all i need to do.