And then, in your Access Database, the column that you wanted to use for your attachement? Is it text, or character (I'm not very familiar with Access data types)?
The thing is, you aren't going to be able to simply bind a file attachment control to a field that uses a text data type. And as far as I know, InfoPath isn't going to allow you to have a submit connection to a database that has a field that would accept an attachment.
Is it absolutely necessary that the attachment be stored in the database? Do you intend (for example) to need to access that field from other applications?