OS X Update: strange checksum problem?

[MuGeN]

Hi guys,

Got a weird problem with an os x update that I would like to understand... I have just put snow leopard on a MBP that I bought second hand (late 2007 model (3,1)) and when I tried to do the software update, it failed... so I tried again, and again it failed...

So... decided to download the combo update (10.6.4) and I couldn't open the dmg as it said the checksum failed, so this seems to also be why I couldn't do it via the automated update process...

Next, I opened the dmg on another mac and it opened just fine, I took out the pkg file and popped that back on the MBP and ran it... now this happens:

Could anyone shed any light on this for me? my CS5 software keeps telling me that I need to update OS X for it to work properly but I cant

 

[MuGeN]

Just done a complete os x reinstall... didn't do a single thing yet except for run software update...

still fails the checksum still fails on the dmg of the combo and the pkg fails

 

[MuGeN]

OK, I thought i'd capture the install log incase that helps anyone make sense of this for me:

Jul  7 11:35:18 MacBook-Pro installd[747]: PackageKit: Install Failed: PKG: extracting "com.apple.pkg.update.os.10.6.4.combo"\nError Domain=PKInstallErrorDomain Code=110 UserInfo=0x10020a540 "An error occurred while extracting files from the package “MacOSXUpdCombo10.6.4.pkg”." Underlying Error=(Error Domain=NSCocoaErrorDomain Code=259 "The file couldn’t be opened because it isn’t in the correct format.") {\n    NSFilePath = "/var/folders/zz/zzzivhrRnAmviuee+++++++++++/-Tmp-/PKInstallSandbox-tmp/Root";\n    NSLocalizedDescription = "An error occurred while extracting files from the package \U201cMacOSXUpdCombo10.6.4.pkg\U201d.";\n    NSURL = "#MacOSXUpdCombo10.6.4.pkg -- file://localhost/Volumes/Mac%20OS%20X%2010.6.4%20Update%20Combo/MacOSXUpdCombo10.6.4.pkg";\n    NSUnderlyingError = "Error Domain=NSCocoaErrorDomain Code=259 \"The file couldn\U2019t be opened because it isn\U2019t in the correct format.\"";\n    PKInstallPackageIdentifier = "com.apple.pkg.update.os.10.6.4.combo";\n}

"The file couldn’t be opened because it isn’t in the correct format."

Any ideas?

EDIT: firmware? not sure how would I check? - although, after googling it a lot of people have had issues with this update