Which version of WireShare are you using?
Finally solved my hardware issues. Tried Win 7 with WSHR 5.6.5 and no problem adding an ip address to the blocked hosts.

Checking the WSHR props file I see:
BLACK_LISTED_IP_ADDRESSES=157.147.90.194;73.121.10 .75
(These were spamBOTs. Note: WireShare automatically blocks these types of spamBOTs so you don't need to add them.)

- Options panel. . . . - Props file listing.

When adding an address to the blacklisted hosts, ensure it is only the ip address and no port or other characters after or before the address. The numbers must be between 0 to 255 and must consist of four parts (#.#.#.#)
Exceptions: (i) using the CIDR format to represent a range such as #.#.#.0/24
(ii) Using the * symbol to represent the full 0 to 255 range. Example: #.#.#.*
(# representing any number between 0 to 255 used here just to represent a number for explanation purposes but this character can not be used with WireShare.)