My daughter's 2 month old MBP froze while she was browsing in Safari tonight. She tried to reboot, but all she got was a flashing question mark inside a folder icon. I googled this and went through the troubleshooting routine in one of the Apple KB articles, which essentially had me boot from the install CD and run Disk Utility to try to repair the HD. Sadly, DU reported the "Invalid B-tree node size" error and told me that it was not able to do any repairs. Does this mean the HD on this MBP is toast, or is there something else I can try before giving it to Apple for a week (which is how long these nincompoops will take, even though it should take them no more than 15 mins to replace the HD)?