Looks like Microsoft Entourage also prevents keyboard input:
(running Leopard and VMware fusion 1.1 build 62573)
$ ioreg -l -w 0 | grep SecureInput
| "IOConsoleUsers" = ({"kCGSSessionSecureInputPID"=1735,"kCGSSessionLoginwindowSafeLogin"=No,"kCGSSessionAuditIDKey"=0,"kCGSessionLoginDoneKey"=Yes,"kCGSSessionSystemSafeBoot"=No,"kCGSSessionOnConsoleKey"=Yes,"kCGSSessionUserIDKey"=501,"kSCSecuritySessionID"=11685424,"kCGSSessionUserNameKey"="xxx","kCGSSessionGroupIDKey"=20,"kCGSSessionConsoleSetKey"=0,"kCGSSessionIDKey"=256,"kCGSessionLongUserNameKey"="XXX"})
$ ps -eaf | grep 1735
501 1735 116 0 1:14.65 ?? 13:41.36 /System/Library/Frameworks/Carbon.framework/Versions/A/Support/LaunchCFMApp /Applications/Microsoft Office 2004/Microsoft Entourage
I stopped Entourage and then I was able to type into my VMware window.