The file sqlceme30.dll is part of SQL Server Compact Edition, which I would assume you are using in your mobile app.
Are you including the proper SQL Server CE dlls in your cab? You might need to add these manually depending on how you create your installer. You need to bundle more than just the System.Data.SqlServerCe.dll file. Here is a link that walks you through the steps to deploy an app using SQL Server CE 3.5: MSDN: How to: Deploy a SQL Server Compact 3.5 Database with an Application
I would also recommend upgrading to SQL Server Compact Edition 3.5 SP1 if you can. You are currently using 3.0. The performance is a little better and the run time is a tiny bit smaller.
If this doesn't help, please include more details as to how you are using the SQL Server CE, and how you are deploying your mobile app.