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This then means that Iguana won’t start. This video shows how to diagnose the issue:
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How do you fix it? A simple safe approach could be to:
Create a new user account
Try out Iguana in it.
If that fixes the problem
Copy the data from your home directory into the new account.
It’s a little more work but safe if you now a power user.
Alternatively you could reconfigure your existing account.