Pinta latest development on Ubuntu 11.10:
1. Open Pinta.
2. Draw something e.g. with Paintbrush tool.
3. File | Save As.
4. In Name filed type in: test
5. From file type drop-down box select: "TGA image" and click Save button.
6. File | Close.
7. File | Open.
8. "Open Image File" dialog opens, selecting a test.tga file and click on Open error is displayed:
Could not open file: /home/[myuser_name]/Pictures/test.tga.
I have tested this on Pinta 1.2 on Windows and TGA files can be normally saved and opened. I have also copied TGA file witch was created by above procedure on Ubuntu and can be normally opened on Pinta 1.2 on Windows. So it looks like Ubuntu specific problem or some regression in development version.