This may be caused by the instability of your broadband network, or it may be caused by Trojan virus. I suggest you kill the virus first, then change your password, and then try changing your signature.

Qq personalized signature is a function extended from Tencent QQ chat software, which was launched by Tencent in 2005. There is a column of personalized signature in QQ personal file. You can set your own unique personalized signature according to your hobbies and mood. When friends chat with you, QQ personalized signature is set on the right side of QQ avatar on the chat window. In every qq account, there are personal data settings, user nicknames (that is, what their names are), and more importantly, personalized signatures.