In Dr. Brown's book he suggests a simple test of giving any rabbi or person fluent in Hebrew the line from Psalm 45:6 in isolation, they will say its:
"Your throne, O G-d, will last for ever and ever"
UriYosef responds:
I would tend to agree with this assessment if and only if this verse is presented to such a person without the rest of the psalm. Presenting the verse by itself removes it out of its correct context. Did you read the entire psalm? (BTW, this is Psalms 45:7 in the Hebrew Bible) When the entire psalm is read by anyone who is fluent in Hebrew and who knows the Hebrew Bible, the conclusion would be rather different.
The common Christian mistranslation of the opening phrase in v. 7{6}, "Thy throne, O God, …", is ruled out by the next verse, v. 8{7} (and the rest of the psalm). Jewish translators and commentators generally render this phrase as "Your divine throne …", or "Your throne of G-d …", or "Your throne is (the throne of) G-d …", or "Your throne, O judge, …" (yes, judges are called "elohim" {e.g., Exod 7:1, Ps 82:6}. These are all acceptable and consistent with the context of the psalm, and point to a mortal king in his role as a ruler, who can be either a historical figure or the promised Jewish Messiah.
The Hebrew phrase כִּסֵּא יהוה - kisse Y-H-V-H, the throne of the L-rd, appears twice in the Hebrew Bible - once at Jeremiah 3:17, where it is a reference to a name by which Jerusalem will be known in the messianic era, and once at 1 Chronicles 29:23, where it refers to King Solomon's throne (given to him by G-d).
I hope this clarifies the matter and demonstrates the false conditions under which the statement to which you have referred was made.

