Connected 2 3560 Catalyst switches via fiber. Network acts flakey some VLANs down

[linda.blaser1]

I have 2 Catalyst 3560 switches.  Several switches in Bldg A, but only one in Bldg B.

I had fiber run between the two buildings.

When I connect the 2 3560's using Fiber/GBIC connectors GLC-SX-MM, the network gets flaky and some of the VLAN even go down.

This is how I have the ports on each end configured:

interface GigabitEthernet0/50

 description ToBuildingX

 switchport trunk encapsulation dot1q

 switchport mode trunk

 switchport nonegotiate

Any ideas?  I'd appreciate any suggestions.

[linda.blaser1]

Now mind you, I don't have the two connected cuz I don't want to bring users down again.

[linda.blaser1]

I forgot to mention.  I swapped the GBIC connectors out just in case one of the connectors in the first pair was bad.  No go.  :(

[ALI ALMHDI]

As you said some vlan down

Before connect the switch make sure

1 the switch in vtp transparent mode

2 make these switches with higher spanning root priority 

3 make sure trunk is up and notice the interface by looking to lights of interface maybe you have a loop in some where 

[Georg Pauwen]

Hello Linda,

in addition to all the other suggestions, and if the fiber cables are not fixed to the GLCs, try and reverse the Tx and Rx pairs.I used to work a lot with these connectors and MM cables in the past, and switching the Tx and Rx pairs sometimes helped...