Make sure your system hard drive has at least 20% free space on it. You can check this in...

...Windows XP by double-clicking My Computer, right-clicking your C: drive, and selecting "Properties." You will a graph of Used space vs. Free Space, and also values for these as well as total capacity. Make sure that the Free Space listed is at least 20% of the Capacity listed.

...Mac OSX by double-clicking your Mac HD and going to Applications > Utilities > Disk Utility. Highlight the Mac HD (in the left-hand column) and choose the "info" button. You will see the Capacity and Free Space in the list that shows up. Make sure that the Free Space listed is at least 20% of the Capacity listed.

If your hard drive does NOT have at least 20% free space, you will need to move some files to a different hard drive, or delete them entirely. A general rule of thumb is this: Anything you INSTALL should go to your SYSTEM drive, and anything you SAVE should go a DIFFERENT drive. Move any of your saved files to your other drive. If you do not have a second hard drive, archive some of your saved files to a CD or DVD, then delete them from the hard drive. Ideally, though, you should be creating and saving ALL Pro Tools sessions to a separate hard drive.

If you have at least 20% free space on your system drive, and still get these errors, try another Knowledgebase solution.