If you are having image caption problems with the WordPress 3.4 upgrade, you might want to check out the WordPress forums. Below is an example of what I described on a particular forum if you need to put up images with captions ASAP, until you can figure out the image/caption problem. Here is the specific forum link for this issue.
From the forum:
The caption looks good in the back end where you write the page/post, but doesn’t translate to the published page. So I capture the image & caption on the writing page/post. I use the Win Snipping Tool to replace the first non-captioned image. Another but more time consuming way would be to capture image with a print screen program and edit in GIMP or Photoshop. So it is like I am uploading an image with the caption already. Takes extra work, but gets it done, and these images will look as the same as future images when the caption problems are resolved.
If there is a need I would be willing to post a video tutorial describing the processes above. Let me know if that would be helpful for you. Contact Otsegoweb