To get around conflicts with "/" in sed, you can use a different delimiter.
In the substitution command, you can simply use any ascii character (except for newline and null) instead of the slash. I generally like to use "|" myself.
sed 's|.*\./\..*||' file #for demonstration purposes, it leaves a blank line behind
You can also change the delimiter for the address fields, except that you must precede the first delimiter with a backslash.
sed '\|\./\.|d' file
Finally, instead of backslash-escaping regex-reserved characters, consider using character class brackets instead. This can often make things more readable, as well as being more proper regex syntax.
sed '\|[.]/[.]|d' file
Here are a few useful sed references.
A couple of regular expressions tutorials: