If I move the Logger line outside of the transactionscope it works fine. So I think it's something to do with this. I'm using SQL Server 2008 r2 for my main database and SQL Compact 4 for my logging database. Also, I've tried adding useTranscations="true".
Was just reading up on the features of SQL Server Compact 4 and noticed that it doesn't support distributed transactions which is basically what you are doing when you write to two different databases in the same transaction.
A solution could be to move your activity log table to your main database, if possible or else I think you'll have to rely on non transacted logging.