Just ran across this when a customer had a couple of raster files that would not display correctly when moving from Microstation SE and I/RAS B SE to Microstation XM / I/RAS B XM. WE had converrted about 60k files from Microstation SE to Microstation XM. Then these files were brought into Projectwsie and the refscan process was applied to rectify the reference file attachments. The problem looked like it was a old tiff format vs a new tiff format, and we had applied the IRASB_TIFF_COVERTER variable and set it to 'old'. This did not seem to fix the problem. The problem showed up as a raster file slightly rotated and streched in one or another dirtection. The raster file disalyed as a raster reference and not a I/RAS B layer. IRASB put information in the message center that gave excellent detailed information on the issue. Apparently the file was originally attached at a angle not exactly at 0,90,180, 0r 270 degrees. When I/RAS B went to open this file it saw this and rejected the attaching of the layer for usage. The message center recommended to define the configuration variable IRASB_SUPPORT_NON_SQUARE_RASTER and set this value to '1' . Once this was done, I/RAS B attached the layer correctly and displayed it correcly also.
I want to thank Jason Gingrich from TSG on assisting me in debugging this issue. Great job, well done !