When FrameMaker inserts a table or a graphic, it creates something called an anchor. This looks like a really bolded upside-down T (
), and it is considered "spaceless". Each table and graphic gets its own anchor, and because they are "spaceless" if you have your cursor on a single line and insert more than one table or graphic without pressing space or return, they are literally layered on top of each other. Also, if there is only the anchor on that line, its symbol can "merge" into the pilcrow and effectively become invisible (
). It sounds to me like this is what is happening with your apparently blank line.
This is why I always put each anchor on its own line with a special tag using a 2-pt font and 0 points above and below, and I usually put a space before and after it to make sure it's visible.
For table positioning, place your cursor in a table cell and then open Table Designer (Table > Format > Table Designer). On the Basic tab, look for Start and make sure it says Anywhere.
For graphics, I generally use the At Insertion Point, which keeps the base of the graphic in the line containing the anchor. Select the graphic and then press Esc-m-p (sequentially, not all at once). That wraps the graphic frame around the graphic and changes the insertion point to At Insertion Point. Note that if the graphic is not on its own line, this will get ugly. If you want to fiddle with this, you can right click on the graphic FRAME (not the graphic itself) and select Object Properties from the pop-up menu. If you're using At Insertion Point, there will be an option to move it above or below the baseline; the other types of anchoring position give you options of Cropped or Floating, and that's what Barb was telling you to look for. You don't want floating unless you want the graphic to stay on the same page no matter what the text does.
To find out if you have more than one anchor on a line, place your cursor at the end of the line (use the End key to be certain), then press the spacebar a couple or four times. Then press the left cursor key ONCE and press the spacebar a couple or four times again. Repeat until you find yourself on the preceding line. If there is more than one anchor on the line, you'll be able to see all of them. Double-clicking to select an anchor will highlight the table or graphic that it anchors, which is how you can identify if they're in the right order.
Some people have no issues putting table and figure anchors as part of a paragraph, but I find it to be more trouble than it's worth.