First question here.  

I purchased Keynote last night and switched to the Purchases tab to watch the download begin (0K of about 434MB).  Immediately the progress bar changed to the Installed button but I saw (via Little Snitch) that bandwidth was still being consumed by storeagent.

Later, storeagent stopped consuming bandwidth and App Store said Could Not Download Keynote: An Error Has Occurred.  In Applications I saw Keynote with its own progress bar empty.

I've tried emptying the ~/Library/Cache for storeagent, signing in and out of the App Store, restarting the Mac (OS X Mavericks) to no avail.

Any ideas?

Here are the most relevant entries from Console:

    6/19/14 6:18:26.767 AM storeagent[401]: *** Assertion failure in
    -[SoftwareInstallOperation _startInstall], /SourceCache/Pisa/Pisa-232.9/iTunes Protocol/Built Into App/SoftwareInstallOperation.m:338
    
    6/19/14 6:18:26.768 AM storeagent[401]: error Error Domain=SoftwareInstallOperation Code=0 "The installation could not be started." UserInfo=0x7faae8fa30d0 {NSLocalizedDescription=The installation could not be started., NSUnderlyingError=0x7faae8fa2c60 "NSInternalInconsistencyException"}
    
    6/19/14 6:18:26.768 AM storeagent[401]: underlyingError Error Domain=SoftwareInstallOperation Code=0 "NSInternalInconsistencyException" UserInfo=0x7faae8fa2c90 {NSLocalizedDescription=NSInternalInconsistencyException, NSLocalizedFailureReason=[PKInstallRequest requestWithPackages:(
        "<PKPackageSpecifier>:\n{\n    URL = \"file:///var/folders/3h/gqqtp7fd5b73ct9c40cbxgqm0000gs/C/com.apple.appstore/409183694/mzps4539971783482202424.pkg#Keynote6.pkg\";\n displayName = TITLE;\n    displayVersion = \"6.2\";\n    identifier = \"com.apple.pkg.Keynote6\";\n    options = 0;\n    version = \"6.2.0.0.1.1341568473\";\n}" ) destination:/] failed}
    
    6/19/14 6:18:26.768 AM storeagent[401]: localException [PKInstallRequest requestWithPackages:(
        "<PKPackageSpecifier>:\n{\n    URL = \"file:///var/folders/3h/gqqtp7fd5b73ct9c40cbxgqm0000gs/C/com.apple.appstore/409183694/mzps4539971783482202424.pkg#Keynote6.pkg\";\n displayName = TITLE;\n    displayVersion = \"6.2\";\n    identifier = \"com.apple.pkg.Keynote6\";\n    options = 0;\n    version = \"6.2.0.0.1.1341568473\";\n}" ) destination:/] failed