change single user to multi user

Hi,

I put the database ABC in single user mode through SSMS, now when I am changing back it to multi user, I get below error

Msg 1205, Level 13, State 68, Line 1
Transaction (Process ID 127) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.
Msg 5069, Level 16, State 1, Line 1
ALTER DATABASE statement failed.

127 is my own session. 

Please help me