I am somewhat embarrassed to have to admit that, while working with It all makes cents's answer, I discovered that I had made a mistake in transcribing my password from my Python code to the original VB.Net code. There was a sequence of two 'w's in the center of the password, one of which was actually lower case, and the other upper. This was not as obvious as it might have been, due to the font which the python editor was using, and I transcribed them both as upper case. The first issue, therefore, was actually a correct response by mariadb when given an incorrect password. However, the second issue (a different exception when attempting to connect with an alternate, and correctly transcribed set of credentials) remains unexplained, and does not occur with the MySQLConnector approach. It all makes cents's answer should, therefore, be regarded as definitive, and, by implication, this connector is to be preferred when linking to a mariadb database from VB.Net.