The + sign means that there is not an even number of blocks. This is normal because a cylinder is not always an integral multiple of block size.
I'm reading this post because I just installed FreeBSD 6.1 and when I was done my Linux fdisk -l showed that all the 3 primaries and extended didn't end on cylinder boundaries. I don't know what happened but a half hour ago this was not showing up on my fdisk -l.
I rebuilt the partition table by hand (not the first time) because I can't stand those messages
Today is my lucky day because everything works fine, all my systems boot and all my data is right where I left it.
I agree with what archtoad said- always make a copy of your fdisk -l ( I do mine in blocks and sectors because I run OpenBSD and now also FreeBSD which like sectors) and get it off the machine you're testing on! If you toast your disk and can't read the file you just saved it doesn't do you any good