invalid integer property 'user' ,what does it mean?

[leokan leokan <gba1991 gmail com>]

Hello,I try to connect a VPN with l2tp issue,but failed.here is the log 

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Oct  7 20:10:56 Notebook NetworkManager[922]: <info> Starting VPN service 'l2tp'...

Oct  7 20:10:56 Notebook NetworkManager[922]: <info> VPN service 'l2tp' started (org.freedesktop.NetworkManager.l2tp), PID 9428

Oct  7 20:10:57 Notebook NetworkManager[922]: <info> VPN service 'l2tp' appeared; activating connections

Oct  7 20:10:57 Notebook NetworkManager[922]: <info> VPN plugin state changed: init (1)

Oct  7 20:10:57 Notebook NetworkManager[922]: <info> VPN plugin state changed: starting (3)

Oct  7 20:10:57 Notebook NetworkManager[922]: <info> VPN connection '中国联通' (Connect) reply received.

Oct  7 20:10:57 Notebook NetworkManager[922]: <warn> VPN connection '中国联通' failed to connect: 'invalid integer property 'user''.

Oct  7 20:10:57 Notebook NetworkManager[922]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.

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my user name is integer,but I can connect this VPN at windows7 using the same user name.how can i fix it?thanks a lot.