I tried all the above solutions, and others from other forums to no avail. it was really annoying because I have another non-Wordpress site where the code worked perfectly. (I was trying to display a Google map in a Wordpress page, but the zoom and Streetview controls were distorted).
The solution I did was to create a new html file (copy paste all the code into Notepad and name it xyz.html, save as type "all files"). Then upload/ftp it up to website, and setup a new Wordpress page and use an embed function. When editing the page go to the text editor (not the visual editor) and copy/type:
http://page URL width="900" height="950">
If you change the dimensions, remember to change it in both arguments above, or you get weird results.
There we go - might not be as clever as some other answers, but it worked for me! Evidence here: http://a-bc.co.uk/latitude-longitude-finder/