There have been a couple so far that have had an issue where 
they need to restart gnudialer the next morning because ...

and it states 

<CampaignName>: Dialing 1 calls (0) skipped
Error selecting leads from mysql! (check table structures)

This is due to a particular (or certain ones) versions of 

a 5.x.x version of mysql.

Please try setting the following variables in an attempt to 
fix the situation.

wait_timeout = 604800 		# 7 days
interactive_timeout = 604800	# 7 days

There are various ways you can set variables and how they 
effect your mysql instance(s), and sessions.  I suggest setting 
a global one, and restarting your mysql.

SET GLOBAL wait_timeout = 604800;
SET GLOBAL interactive_timeout = 604800;

Then *restart* mysql.


***********************************************************
These are generic EXAMPLES for how to set those various 
methods of instance(s), sessions.
***********************************************************
SET sort_buffer_size=10000;
SET @@local.sort_buffer_size=10000;
SET GLOBAL sort_buffer_size=1000000, SESSION sort_buffer_size=1000000;
SET @@sort_buffer_size=1000000;
SET @@global.sort_buffer_size=1000000, @@local.sort_buffer_size=1000000;