enable MPLS + OSPF can't ping

Dear Sir,

We have setup the OSPF, MPLS and iBGP to connect the 3 router, we found the strange problem, if enabled the mpls on R3, we can’t ping to R2:10.255.255.2, but R2 can ping to R3:10.255.255.3.
If disabled the mpls on R3, R3 can ping to R2:10.255.255.2 and R2 can ping to R3:10.255.255.2?
anyone can help?
mpls.png
TungHo

Make sure LDP is enabled on your loopback interfaces - it sounds like one of the loop interfaces isn’t getting an LSP built between R1 and R3.