While trying to open the project, I got the following error.
"...A reference to the type converter 'SD.LLBLGen.Pro.TypeConverters.DecimalConverter' was found, however this typeconverter wasn't loaded / found
Do you want to specify the additional type converter folder for this project and retry?..."
And actually there is a folder which contains the class DecimalConverter: C:\...\SAME_PROJECT_FOLDER\TypeConverters\DecimalConverter.cs
However, this doesn't help with this error, I still have the same error and the project cannot be opened.