Continually getting the same error in logs

First I tried deactivating the plug-in any errors still occurred. So I completely erased the plug-in and cleared all my cashes and the errors still occur. Any thoughts? I thought by deleting the plug-in that would solve the problem

I first deactivated it and that did not fix the problem. So I deleted it through the dashboard by going to the plug-in page and clicking delete. I was looking at my database in myPHPadmin and there are some tables that I think are from the plug-in. But I am not sure. I contacted the plug-in administrator to find out if those tables are related to the plug-in. Thanks any help would be greatly appreciated. I am completely stumped

These are the errors I keep getting:

[Sun Nov 03 03:29:59 2013] [error] [client 23.92.28.9] WordPress database error Table ‘wrd3.wp_data’ doesn’t exist for query SELECT * FROM wp_data made by require(‘wp-blog-header.php’), require_once(‘wp-load.php’), require_once(‘wp-config.php’), require_once(‘wp-settings.php’), include_once(‘/plugins/dhtmlxspreadsheet/spreadsheet.php’), sh_load_dump
[Sun Nov 03 03:29:59 2013] [error] [client 23.92.28.9] WordPress database error Duplicate entry ‘demo_sheet’ for key ‘PRIMARY’ for query INSERT INTO wp_dhx_sheet VALUES (‘demo_sheet’, null, null, ‘any_key’, null) made by require(‘wp-blog-header.php’), require_once(‘wp-load.php’), require_once(‘wp-config.php’), require_once(‘wp-settings.php’), include_once(‘/plugins/dhtmlxspreadsheet/spreadsheet.php’), sh_load_dump
[Sun Nov 03 03:30:00 2013] [error] [client 23.92.28.9] WordPress database error Table ‘wrd3.wp_data’ doesn’t exist for query SELECT * FROM wp_data made by require_once(‘wp-load.php’), require_once(‘wp-config.php’), require_once(‘wp-settings.php’), include_once(‘/plugins/dhtmlxspreadsheet/spreadsheet.php’), sh_load_dump
[Sun Nov 03 03:30:00 2013] [error] [client 23.92.28.9] WordPress database error Duplicate entry ‘demo_sheet’ for key ‘PRIMARY’ for query INSERT INTO wp_dhx_sheet VALUES (‘demo_sheet’, null, null, ‘any_key’, null) made by require_once(‘wp-load.php’), require_once(‘wp-config.php’), require_once(‘wp-settings.php’), include_once(‘/plugins/dhtmlxspreadsheet/spreadsheet.php’), sh_load_dump

Yes the site works but I am having issue with a different plug-in (postie). I get an internal error message when I click on links generated by the postie plug-in. It was suggested that I try and correct the errors to see if they corrected the issue with the plug-in. Even though the plug-in causing the errors are a completely different plug-in. It didn’t make sense to me, but I thought I would give it a try since nothing else I am doing is working

The error log is from my host. When I get the internal error message it says:

500 internal server error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator, and inform them of the time the error occurred, and anything you might have done that may have caused the error.

More information about this error may be available in the server error log.

You gave me those two errors saying that they repeat continually throughout the error log and to try and fix them. Saying maybe that was the cause of the problem.

Is there a way for me to find out specifically what the internal error is?

Thanks for all your help I appreciate it