Hi jnd3344, and a warm welcome to the forums.
I'm afraid "invalid node count" errors can at times be very difficult to fix. They indicate a serious problem with the organisation of the disk's structures.
Sometimes the third party utility
"DiskWarrior" is able to repair them satisfactorily without you having to wipe the drive and repartition and reformat it. It is the best option to try first if you can. (If you already have a different third party utility, such as Drive Genius or TechTools pro you could try that instead, but DiskWarrior is certainly the best of the options at this particular task).
Sometimes however, even DiskWarrior is unable to repair this issue. The next step is to wipe the drive by re-partitioning and reformatting it using Disk Utility. This , of course, will remove everything from the drive so first boot up from an external drive and save as much as possible from the internal one if it contains things you need, and then re-install the OS and your applications etc. You may even be able to actually clone the contents of the internal drive to an external drive using
Super Duper but when "invalid node structures" exist on the internal it is likely that at least some files will later prove to have become corrupted.
On rare occasions even simply wiping the drive isn't sufficient and it is necessary to use the option to "zero" the drive as well. There is also a chance that the problem has been caused by a developing hardware failure of the drive itself. If this is the case , I'm afraid, you may not be able to repair it at all, and even if you can, it may recur before too long. A good utility for testing the integrity of the drive hardware is "Smart Utility" from
Volitans software.
All of the above assumes that you are out of warranty and don't have extended AppleCare coverage. If you do, then you might want to consider simply backing up as much of your drive as possible while booted from an external drive, and leaving the underlying problem for Apple to fix. In such a situation, if it doesn't respond to simply erasing and reformatting, it is quite likely that they would simply replace the drive.
Sorry all of the above sounds a bit draconian. There is a good chance that one of the more basic approaches (using DiskWarrior or wiping the drive and repartitioning / reinstalling) will fix it, but invalid node errors can be a real pain in the proverbial to fix at times.
Please do ask if any of the above doesn't make good sense or if you have follow up questions.
Good luck and best wishes
Rod
