I have a huge table set in LaTeX, and for some reason I get a blank page first when I typeset it. I have found that the cause is in one of the header rows, but not why. The row in question has a series of multicolumn spans, see below.

The document looks like this: (I shortened the code for space, it covers all the months, and each month covers 2 columns)

the problem is in the line that starts with "&\multicolumn{2}".

Why do you need the leading "&" in that line? (It begins a row dosn't it?)
How do you know this is the problem: you remove the line and the empty page goes away?

If you remove the \title{} and \author{} ... do you still get the empty page?

the '&' is because the "january" doublecolumn starts at column 2, with row headers in the first. I have tried removing it, no success, the cells are just moved one position to the left. removing author and title changes nothing. commenting out the entire line fixes the problem, but that is not an option.

solved, I needed to change \textheight to be higher than the whole table. I also changed the \textwidth to remove a badbox warning.

well done - and error output is always useful to include.

Usually you get a blank leading or trailing page when something is too big in some way ... my initial thought was that you table seems to full the whole page so a \title wouldn't fit there too ... the title would end up on the first page with the table on the second, and, since the title was a blank the page would be a blank.

As it happened, the table was too big for the page it was on - it gets shunted to the next page, and overflowing the box.

It is normally bad form in latex to adjust the textheight, width and margin-sizes. Your table really needs to go across two pages