Go to Windows-->Styles-->Table styles and Cell styles, check the settings there make them as you wanted , may be default settings are getting applied on the line when you delete the last row.
It works fine at my end..Which Indesign veriosn are you using and in which OS
Have you tried creating the new table in the fresh new document and checked ,,,does it behave in teh same manner.
My suspicion would be that you have a Table style applied that has a border onthe bottom row, and that the style was aorigianlly overridden to remove it. Dleting the last row would remove the overridden cells, and the bortder would re-establish, but that's just a guess.
It only seems to appear when I have set up alternative strokes on the columns or rows. If I delete a row or column at the end with alternative fills applied it looks fine with no strange line. It happens everytime I use tables in Indesign, has done since I can remember. When I look at the table styles it just has the default basic table setup. I'm using CS3.
If you want to post the file somewhere, one of us will take a look and see if we can figure it out. I'm doing Kithcen renovations this week, myself, so It won't be until I knock off for the day for me, but one of the others may be able to give you a faster answer.
Here is a test file, you can see when I have deleted either a row or column at the end it has created a thick black line.
I've got the file, but I'm not sure what you are trying to show me. It's a single frame with a blank table. The table has a 1 point stroke applied as the right and bottom border.
In order to help you I'm going to need to see the file the table that is giving you a problem. I'll need to have it as you want it it to appear so that I can try to delete a row and see what happens. It does no good if you've already deleted the row and not reset the strokes.
Okay here is the table that I am actually trying to edit and delete rows and columns. I have left it without deleting anything so you can see if the lines appear when you delete the last row or column.
While you would do well to actually set up a custom set of cellstyles and a table style for this, I was able to solve the problem in your file by going to Window > Type and Tables > Table Styles, then selecting the [Basic Table] style, right clicking and choosing Edit [Basic Table]. Under Table Setup change the Table Border specifications so the stroke type is explicitly set to None. For some reason setting the weight to 0 is not sufficient here.
Checked you file and when we delete the row at the bottom the table border get added at the bottom ,
Select your table ,
Go to Table-->Table options-->Table Setup
In the dialog box , You will have a option under "Table border" :- "Weight" , which would be blank, enter "0 pt" in it and Click "OK"