Originally Posted by steinarb
when I try to read it in my Sony PRS T-1 reader, the reader immedately returns to the Home menu.
Kovid is correct here about Sony readers. My reader is unforgiving with less than perfect ePubs. I've generally only caused imperfections by using Tweak Book, (not had any problems directly from calibre conversions), and have had symptoms similar to those you describe.
Having spent some time tweaking I was reluctant to lose my efforts by doing another conversion so I checked my book at ePub Validator http://validator.idpf.org/
which located the problems with pinpoint accuracy. The output can be a bit verbose but it certainly shows what's wrong.
This may give you a means of fixing your own ePubs and also the info necessary to see whether a change in calibre is required.