Asterisk originate not working

I am trying to make vtiger work with asterisk 1.6 (freepbx server). I have managed to get to the point where I can connect to the asterisk manager interface (AMI) and write to it. But for some weird reason, the originate would not work. I am using -

Action: Originate
Channel: SIP/2000
Exten: 1000
Context: from-internal
Priority: 1
Callerid: 2000
Async: yes

I tried reading the responses from AMI after making a direct call and it always had a random number after the channel. For example -

Event: Dial
Privilege: call,all
SubEvent: Begin
Channel: SIP/1000-0000000c
Destination: SIP/2000-0000000d
CallerIDNum: 1000
CallerIDName: 1000
UniqueID: 1359790601.12
DestUniqueID: 1359790601.13
Dialstring: 2000

Can this be an issue or am I missing anything here? Any pointers would be most helpful. Would be happy to provide any details.

Solution

I managed to fix the issue, so here is how the debugging went -

started asterisk CLI using asterisk -rvvv
used a CLI originate command

channel originate SIP/1000 extension 2000@from-internal
step 2 showed an error on the extension being busy (error 486 to be specific).
googled error to find out that the extension 1000 is being used by a hard phone and that can cause issues
changed the manager extension to 2000 in manager.conf and tried making the call using

channel originate SIP/2000 extension 1000@from-internal
step 5 worked, but calls from PHP still failed. added debugging to find that the AMI was returning a permission denied
found out that from 1.6 onwards you need to have originate in the manager.conf read/write options

Now it works perfectly fine. Hope this helps someone, though I think this case might be a very personalized issue.