I had this problom too. the way that i solved it was to put the computer "bad" into target disc mode, (hold "T" when restarting) and get another computer "good" (mid 2009 macbook pro) or must be able to boot 10.6 disc. conect both computers via firewire, put the disc in computer "good", restart, boot from 10.6 instal DVD (hold option key on restart) open disk utility and it will let you erase the computer "bad" drive.
I had a similar issue, so for anyone doing a web search:
not able to delete linux swap partition using disk utility in Mac OS X
note: i do not have LVG. this is on a late 2012 mac mini
my linux swap partition was not mountable (grayed out in the disk utility menu) and i had a 500 GB hdd with 200 GB for Mac OS, 16 GB for Ubuntu, and the rest was free space. I could not access the free space as it was part of the partition with linux swap. I added debug option to disk utility (look that up, I'm not sure if it helped at all). Then with the linux swap partition selected, i went to the 'erase' tab and erased it. That made everything but Mac OS free space. Then with the high HDD selected, the disk not the volumes on it, I was able to resize Macintosh HD in the Partition tab.
I hope this helps
Thanks to all the previous posters for your help