MI Things that move

[TGM Alexandroupoli]

Hi all you MI experts,   my problem is as follows. I 've registered some topo maps as raster images and I 'm digitizing over them, in a new table. The thing is, as I zoom in or out, or when I close a raster image or open a new one, all my digitized data are moving! They seem to be OK, but when I do something and my screen refreshes, my polylines move to different directions.   Any clues or ideas? Thanks in advance   Iason Papazachos Computer Geologist TGM SA Alex/poli, Greece