MASTER OT J045804.40+212306.8
It appears MASTER OT J045804.40+212306.8 is not a CV after all. It is a Jovian satellite! John Greaves must have had quite a smile on his face when he informed the MASTER team of this error. They quickly published a retraction on ATEL.
"MASTER OT J045804.40+212306.8 (ATel #4428) is the Jovian satellite J6 Himalia (John Greaves, private communication). We are very sorry."
I'm quite disappointed to realize not everything posted to the Internet is true...