I have a 10 Gb ECW file (mosaic of a whole county) that is in Oblique Stereographic projection with Datum: Dealul Piscului 1970. The problem was that no matter the Default CRS for new project was, when I wanted to add this raster the coordinates were all wrong, although the input projection for the raster was correct. This problem was solved by deleting the ECW's ".xml" file that was accompanying the ECW file. Once deleted, the problem was solved and the QGIS was showing the right coordinates.
Once the above problem was solved. I wanted to add a vector layer of 30 mb that represents the whole waterway of the Danube Delta plus inland towns. This layer is in WGS84. Now when I try to import this layer does not overlay with the ECW file. The ecw file have been defined with the right projection also the vector layer have been defined with the right projection. In settings/options/CRS/ the "on the fly" is checked and the project projection is WGS84 and also tried the vice-verse with Oblique Sterographic Dealul Piscului. With all the permutations available I still can not overlay the layers.
Do you have any other suggestions?