Determining which NTLM version is used

You can find which NTLM version is used in your registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA\LMCompatibilityLevel.

Once you have the registry open, determine the value data (0 - 5):

Level	Group Policy Name	Sends	Accepts	Prohibits Sending
0	Send LM and NTLM Responses	LM, NTLM	NTLMv2 Session Security is negotiated	LM, NTLM, NTLMv2 NTLMv2 Session Security (on Windows 2000 below SRP1, Windows NT 4.0, and Windows 9x)
1	Send LM and NTLM---use NTLMv2 session security if negotiated	LM, NTLM NTLMv2 Session Security is negotiated	LM, NTLM, NTLMv2	NTLMv2
2	Send NTLM response only	NTLM NTLMv2 Session Security is negotiated	LM, NTLM, NTLMv2	LM and NTLMv2
3	Send NTLMv2 response only	NTLMv2 Session Security is always used	LM, NTLM, NTLMv2	LM and NTLM
4	Send NTLMv2 response only/refuse LM	NTLMv2 Session Security	NTLM, NTLMv2	LM
5	Send NTLMv2 response only/refuse LM and NTLM	NTLMv2, Session Security	NTLMv2	LM and NTLM

^{Source Microsoft TechNet Magazine}

More detailed discussion can be found here.

Currently Sharepoint plugin can only work with NTLM authentication.