New one! "The User Profile Service failed the logon. User profile cannot be loaded."

OK,so I've encountered varying ways that a windows profile doesn't load, or loads a backup and it seems like data is lost when it isn't, and when you can't login to a domain but pull network cable and all is fine... but this is a new one...

If you run into this specific login error:  "The User Profile Service failed the logon. User profile cannot be loaded."

Follow these steps below. Worked like a charm.

I would HIGHLY recommend to add as the very first step... to copy the profile from the c: drive when logged in as a local administrator before making registry changes.  That way in case something goes ary, the data file are still available.

My guess is that in some cases this is caused when a local antivirus scan doesn't release before the profile fully logs off during a standard  shutdown process...
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From spiceworks posting:

"The User Profile Service failed the logon. User profile cannot be loaded."

Appears while attempting to logon in Windows Vista, 2008, 2008 R2 and 7.

Exact cause is unknown, but this issue may occur if the user profile was manually deleted by using the command prompt or Windows Explorer by a user or by some program. A profile that is manually deleted does not remove the security identifier (SID) from the user profile list in the registry. Since the SID is still present, Windows will still try to load the profile by using the ProfileImagePath that points to a nonexistent path. Therefore, the profile cannot be loaded.

This can also be a issue with the user profile entering into a backup state, or if the C:\Users\(User Name) user profile folder is manually renamed.

1. Log on to the Computer

Log on to the computer using the Administrator (or an Administrator-level) account.

If the computer is not joined to a domain, reboot it and start your computer in safe mode, then log on using the Administrator (or an Administrator-level) account.

2. Trawl through the Registry

Open the Start menu. In the Start Search area, type regedit and press Enter (if prompted by UAC, click Continue/Yes). In regedit, go to:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList

Expand the ProfileList key and look for the SID key (named "S-1-5"...) with a long number that ends in ".bak". Click it, and look at the ProfileImagePath value in the right pane to verify that this is the user account profile that has the error.

a) If you have two SID keys with the same number (with one ending in ".bak" and one showing the affected user account in the ProfileImagePath value), continue to Step 3;
b) If you have just one SID key with the ProfileImagePath value showing the affected user account, proceed to Step 4.

3. Two SID keys with the same number

a) Of the two SID keys that corresponds to the affected user account, right-click the SID key that does NOT end in ".bak" and click Rename.
b) Add .bk to the end of the numbers and press Enter.
c) Right-click the other SID key that DOES end in ".bak" and click Rename.
d) Remove only .bak from the end of the numbers (so that it has the same name as the other SID key did before you renamed it) and press Enter.
e) Now go back and Rename the first one with .bk to .bak now at the end of the numbers and press Enter.

Proceed to Step 5...

4. Only one SID key ending in ".bak"

a) Right-click the SID key that corresponds to the affected user account and click Rename.
b) Remove only .bak from the end of the numbers, and press Enter.
c) In the right pane, right-click the RefCount value (if none exists, right-click the right pane and click New and DWORD (32 bit) Value, then type RefCount and press Enter), and click Modify.
d) Type 0 into the Value Data textbox and click OK.
e) In the right pane, right-click the State value and click Modify.
f) Type 0 into the Value Data textbox and click OK.

5. Try logging on again!