Error in SP2013 when a custom .wsp tries to bring data from database

Hi All, i have a very particular problem with a .wsp. I ´ve developed a webpart to search data on a MySQL database.

The .wsp worked fine until i realized that different instances of the webpart where sharing the custom properties. The problem was that those properties where developed like this:

private static string dataBase;

[WebBrowsable(true),
WebDisplayName("Database"),
WebDescription("Database"),
Personalizable(PersonalizationScope.Shared),
Category("DB Connection")]
public string _dataBase
{
   get { return dataBase; }
   set { dataBase = value; }
}

And the answer was declaring those properties like this:

[WebBrowsable(true),
WebDisplayName("Database"),
WebDescription("Database"),
Personalizable(PersonalizationScope.Shared),
Category("DB Connection")]
public string dataBase
{
   get;
   set;
}

But like this, when the webpart try to read from the database, it gives an error in the Sharepoint site. The error doesn´t say anything important, and in the errors log it says that the database doesn´t exists which isn´t true.

The connection is made successfully to the database, but when i try to define a datareader occurs the error. The line when this happens:

MySqlDataReader dataReaderDB = commandByDateDB.ExecuteReader();

ADDITIONAL DATA:

If the connections variables are hardcoded as private

private string dataBase = "mydatabase";

the webpart works.

Another data is that i´ve two servers with SP2013, one for development with the Visual Studio 2012 installed, and another for testing, without Visual Studio 2012. The problem ONLY occurs on the testing server, and i cant install VS2012 on the testing server to debug the error (due to administration decisions)

Any help to give an end to this problem will be great.

THANKS IN ADVANCE