Hmm
Have you run a repair disk permission?
Any mounted drives in finder that you don't need or can unmount while testing?
Could a recent file on a volume that is inaccessible causing a pause?
Finally you could select FCPX as a "Target" and run it through Instruments->OSX->File Activity scheme to see what files it is reading and writing during the big pause. Instruments is part of xCode.
Couple of updates (still downloading XCode):
Console shows these after FCPX finally launches:
3/13/14 12:04:48.952 AM WindowServer[3709]: disable_update_timeout: UI updates were forcibly disabled by application "Final Cut Pro" for over 1.00 seconds. Server has re-enabled them.
3/13/14 12:04:49.208 AM WindowServer[3709]: common_reenable_update: UI updates were finally reenabled by application "Final Cut Pro" after 1.26 seconds (server forcibly re-enabled them after 1.00 seconds)
and, if I force quit FCPX before it starts actually launching (when it just shows this but no words to show it's loading:
the error report includes this:
Date/Time: 2014-03-13 00:09:04 -0500
OS Version: 10.9.2 (Build 13C64)
Architecture: x86_64
Report Version: 18
Command: Final Cut Pro
Path: /Applications/Final Cut Pro.app/Contents/MacOS/Final Cut Pro
Version: 10.1.1 (240682)
Build Version: 1
Project Name: ProEditor
Source Version: 24068002033000000
App Item ID: 424389933
App External ID: 299842652
Parent: launchd [170]
PID: 4522
Event: hang
Duration: 0.99s (process was unresponsive for 11 seconds before sampling)
Steps: 10 (100ms sampling interval)
Hardware model: MacPro6,1
Active cpus: 16
Fan speed: 790 rpm
Free pages: 6324111 pages (-1998)
Pageins: 0 pages
Pageouts: 0 pages
Swapins: 0 pages
Swapouts: 0 pages
Process: Final Cut Pro [4522]
Path: /Applications/Final Cut Pro.app/Contents/MacOS/Final Cut Pro
Architecture: x86_64
Parent: launchd [170]
UID: 501
Task size: 26606 pages
Note: Unresponsive for 11 seconds before sampling
Thread 0x47b42 DispatchQueue 1 priority 47
10 start + 1 (libdyld.dylib) [0x7fff827ef5fd]
10 NSProApplicationMain + 333 (ProKit) [0x101730f6a]
10 -[NSApplication run] + 553 (AppKit) [0x7fff81b7db2c]
10 -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] + 122 (AppKit) [0x7fff81b89a2b]
10 _DPSNextEvent + 1026 (AppKit) [0x7fff81b8a246]
10 AEProcessAppleEvent + 56 (HIToolbox) [0x7fff85241161]
10 aeProcessAppleEvent + 315 (AE) [0x7fff83dc3b36]
10 dispatchEventAndSendReply(AEDesc const*, AEDesc*) + 31 (AE) [0x7fff83dc3c32]
10 aeDispatchAppleEvent(AEDesc const*, AEDesc*, unsigned int, unsigned char*) + 381 (AE) [0x7fff83dc3e1f]
10 _NSAppleEventManagerGenericHandler + 106 (Foundation) [0x7fff81516d7d]
10 -[NSAppleEventManager dispatchRawAppleEvent:withRawReply:handlerRefCon:] + 294 (Foundation) [0x7fff81516f0a]
10 -[NSApplication(NSAppleEventHandling) _handleCoreEvent:withReplyEvent:] + 242 (AppKit) [0x7fff81b8e36b]
10 -[NSApplication(NSAppleEventHandling) _handleAEOpenEvent:] + 570 (AppKit) [0x7fff81b8e916]
10 -[NSApplication _sendFinishLaunchingNotification] + 195 (AppKit) [0x7fff81b91a2c]
10 -[NSApplication _postDidFinishNotification] + 289 (AppKit) [0x7fff81b91cf9]
10 -[NSNotificationCenter postNotificationName

bject:userInfo:] + 68 (Foundation) [0x7fff814f87ba]
10 _CFXNotificationPost + 2893 (CoreFoundation) [0x7fff8ccffa6d]
10 __CFNOTIFICATIONCENTER_IS_CALLING_OUT_TO_AN_OBSERVER__ + 12 (CoreFoundation) [0x7fff8ce0be0c]
10 -[PEAppController applicationDidFinishLaunching:] + 1055 (Final Cut Pro) [0x10142364f]
10 -[PEAppController _migratePreGodzillaColorPresets] + 40 (Final Cut Pro) [0x101423218]
10 +[FFColorLooksList migrateColorPresets:] + 246 (Flexo) [0x1022c8e26]
10 +[FFStorageManager moviesURL] + 69 (Flexo) [0x101ddcd15]
10 +[FFStorageManager sharedInstance] + 52 (Flexo) [0x101ddb0d4]
10 -[FFStorageManager init] + 221 (Flexo) [0x101ddb21d]
10 -[FFStorageManager refreshAvailableVolumesAlwaysWarnForPath:] + 50 (Flexo) [0x101ddf792]
10 -[FFStorageManager newAvailableLocationsWithLegacyBehavior:alwaysWarnPath:] + 1907 (Flexo) [0x101ddf643]
10 -[FFStorageManager locationFromVolumePath:volumeRefNum:diskUUID:networkPath:alwaysWarnPath:] + 138 (Flexo) [0x101ddeeaa]
10 -[FFStorageLocation isTimeMachineVolume] + 107 (Flexo) [0x101dd9aab]
10 -[NSFileManager fileExistsAtPath:isDirectory:] + 126 (Foundation) [0x7fff8150afdf]
10 lstat$INODE64 + 10 (libsystem_kernel.dylib) [0x7fff80d9f70a]
*10 hndl_unix_scall64 + 22 (mach_kernel) [0xffffff80002f3b26]
*10 unix_syscall64 + 499 (mach_kernel) [0xffffff800063e363]
*10 lstat64 + 156 (mach_kernel) [0xffffff80003e936c]
it goes on and on, but I can post the rest if anyone thinks it might help.
Again thanks for looking! It's driving me crazy.