Problem with GPO / GPP (drive mapping) when L2 authentication is in place

Issue:
We have problem with Drive Mapping (Group Policy Preference, Item level targetting). Drives are not mapped to users after restart of computer.
Tests proved:
- this problem occurs only on ports where L2 authentication (computer certificate) is enabled
- if user login immediately (if there is 10+s delay with logon then disks are mapped properly)
- from GPO logs (compared logs with and without L2auth) is obvious that when computer is connected to switch with L2 auth then, due to delays, user's GPO is applied BEFORE computer GPO ... this I do not understand at all

Details:
If mapped drives are set to Update ... they are in disconnected state after restart (red X) ... but after 20-30s it is possible to see the content (but red X remain)
If mapped drives are set to Replace ... they are not visible after restart

... if user does Logoff/Logon disks are properly mapped

Settings of drive mapping (example of user policy):
Action: Update
Location: DFS folder
Reconnect: Enable
Use first Available: Disabled
Run in logged on user's security context: Yes
Item level targetting: Security Group

(Computer policy)
Always wait for the network at computer startup and logon: Enabled

Here is description of our environment:
DC: W2k8 R2
Clients: Windows 7 x86
L2 Auth: Computer Authentication, MS Supplicant set in computer policy

Any idea how to solve this issue??? And how user's GPO could be applied before computer GPO??

Thank you.

Michal