In QGIS, I am getting an error message every time I edit a node. Also, there is a lot of lag in performance. The message is:

"Transform error caught: forward transform of (10990.308086, 100347.255186) PROJ.4: +proj=longlat +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +no_defs +to +proj=utm +zone=54 +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs Error: latitude or longitude exceeded limits"

I hae been very careful to Set Layer CRS on all layers, to GDA94, or, in the case of the two raster layers, GDA94/MGA zone 54 (which is also the project CRS). This should all work. Shouldn't it?

But it is odd, that when I was using my legacy MapInfo TAB layers, they would show up in QGIS with weird projections that were not the projection in the TAB files, like some old Dutch projection and, more usually, NAD projections. I saved those layers as SHP files (resetting the projection to GDA94) to see if QGIS works better with SHP. And it did, for a few hours. Now the error messages are back. What is wrong? Is this a QGIS bug? Or is there a backoffice setting that I've missed?