I know it has beena while since this post but I'm curious if you ever found a solution to this problem?

Which drivers are you trying to inject? All of the WinPE CAB or just a NIC driver?

"I know it has beena while since this post but I'm curious if you ever found a solution to this problem?"

The solution was not to use the x86 boot image and not the x64 one!

"Which drivers are you trying to inject? All of the WinPE CAB or just a NIC driver?"

It is a long time ago, but I think it was only a problem with some NIC drivers.

"Which drivers are you trying to inject? All of the WinPE CAB or just a NIC driver?"

Here is a CP of what I posted in another thread at a different board.

Error: Failed to import the following drivers:
DELL CERC SATA 1.5/6ch RAID Management Device - Failed to inject a ConfigMgr driver into the mounted WIM file

This is just one of many drivers I am having this problem with. If I take this exact same driver, copied from the very place this process is using, and manually add it to the image using DISM with the /forceunsigned flag it works without a problem. After some digging there is a log file created by DISM during the image build using SCCM located at C:\Windows\Logs\DISM\dism.log. In this log I get the following error.

2010-11-12 12:47:38, Info DISM DISM Driver Manager: PID=6024 Signature status of driver \\vsccm\Source\Drivers\Dell\PE\Dell-WinPE-Drivers-A02\winpe\x64\Storage\R129526\cercsr6.inf is: UNSIGNED - CDriverPackage::InitSignatureStatus
2010-11-12 12:47:38, Error DISM DISM Driver Manager: PID=6024 Cannot install non-signed boot-critical drivers on amd64 images. Use /forceunsigned switch to override. \\vsccm\Source\Drivers\Dell\PE\Dell-WinPE-Drivers-A02\winpe\x64\Storage\R129526\cercsr6.inf - CDriverManager::CheckClientAddDriverScenarios(hr:0x80070032)
2010-11-12 12:47:38, Error DISM DISM Driver Manager: PID=6024 d:\w7rtm\base\ntsetup\opktools\dism\providers\dmiprovider\dll\drivermanager.cpp:1063 - CDriverManager::Internal_DoAddDriverPackage(hr:0x80070032)
2010-11-12 12:47:38, Error DISM DISM Driver Manager: PID=6024 d:\w7rtm\base\ntsetup\opktools\dism\providers\dmiprovider\dll\drivermanager.cpp:519 - CDriverManager::ExecuteCmdLine(hr:0x80070032)
20

Thanks for posting the details on your issue with the WinPE driver CAB. I'll forward to the product team.

WinPE A04 has been released. We have optimised the number of drivers in the winPE cab.