This is weird! When i changed my computer date, suddenly i can’t send message in conversation. To solve this issue, first download SQLiteBrowser for Windows
http://sourceforge.net/projects/sqlitebrowser/?source=typ_redirect
Then, go to :
1 | C:\Users\<Your User>\AppData\Roaming\Skype\<your-skype-account> |
Edit “main.db” with SQLitebrowser. Go to browse data and select messages.
Now delete messages that more than the date in your computer. Solved!