Oracle SQL Developer: Can't edit in SQL Worksheet

Problem:

In SQL Worksheet you cant edit or use back space.
This may happen on newly installed Oracle SQL Developer.

Solution:

Go to  Tools | Preferences | Accelerators and press  Load Preset.
Then it'll  load the default preset.
Then try again to edit.

Virtual Box Error - VT-x features locked or unavailable in MSR.

Error:

Failed to open a session for the virtual machine

VT-x features locked or unavailable in MSR.
(VERR_VMX_MSR_LOCKED_OR_DISABLED)

The details are:

Result Code:
E_FAIL (0×80004005)
Component:
Console
Interface:
IConsole {1968b7d3-e3bf-4ceb-99e0-cb7c913317bb}



Solution:

You have to change the processor Number to get rid of this error.

So go to vitual-Box Machine–>setting–>system–>Processor–> change the CPU No. to 1.
Then restart the VM and it'll work.