Do you only receive achievements for campaign missions if you complete them without using the save game feature. I completed a couple last night but had to restart from a last save point when I died. I completed the missions along with all the optional objectives but never got the achievements.
I don't think so. I also had the save game issue after the patch but I loaded a game in the hyperion and it was good. used a lot of saves, I actually fell about a couple attacks short of getting the hard achievement for "A Sinister Turn" so i loaded an autosave and finished the mission from there(and got the achievement also)
It has to do with with the a Starcraft2 patch
From the Starcraft2 forums:
Anyone who had a saved game before today[sic before patch] will not get achievements for that mission. Brilliantly to play a saved game which is old (patch wise) SC2 throws you off of Battle.net to play the mission without the new updates... and since you're not on Battle.net you won't get the achievements.
That may be a bug with the latest patch. I've heard many reports of various problems with campaign saves.
Prior to the patch (haven't played campaign since) I have always received achievements with liberal usage of saves. The patch notes have no indication that that would have changed.
Also, maybe obvious but make sure you're not playing offline mode (unlikely as if I remember correctly the mode is only available when you don't have an internet connection)