google_ad_client = "pub-1234567890";
/* 160x600 ink, created 5/26/10 */
google_ad_slot = "0987861562";
google_ad_width = 160;
google_ad_height = 600;
To fix it, simply remove <!-- and //-->.
An alternative is to insert the Adsense code in the individual post because Blogger leaves the formatting as it is, but it might be a hassle to do this for every post
If you have any questions let me know and I will do my best to help you!