What happens if you go to "Get Info" on Zotero and check "Open in 32-bit mode"? Does it run then, or do you get the same error?

I have tried opening Zotero standalone in ' Open in 32-bit mode' but it does not load and gives a rather long error message as reported by nialdhodson above.

Process: zotero [200]
Path: /Applications/Zotero.app/Contents/MacOS/zotero
Identifier: org.zotero.zotero
Version: 2.1a2 (2.1.0)
Code Type: X86 (Native)
Parent Process: launchd [90]

Interval Since Last Report: 62 sec
Crashes Since Last Report: 1
Per-App Interval Since Last Report: 3 sec
Per-App Crashes Since Last Report: 1

Date/Time: 2011-01-16 08:12:40.117 +0530
OS Version: Mac OS X 10.5.8 (9L31a)
Report Version: 6
Anonymous UUID: 44C2FD8C-C1B8-4B4D-ADCB-FEF7EBFED1D9

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x000000000ccc9108
Crashed Thread: 0

Thread 0 Crashed:
0 ??? 0x0ccc9108 0 + 214733064
1 ??? 0x0ccc9649 0 + 214734409
2 dyld 0x8fe12f36 ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) + 246
3 dyld 0x8fe0e7e3 ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int) + 307
4 dyld 0x8fe0e8c9 ImageLoader::runInitializers(ImageLoader::LinkContext const&) + 57
5 dyld 0x8fe02202 dyld::runInitializers(ImageLoader*) + 34
6 dyld 0x8fe0b64a NSLinkModule + 314
7 libSystem.B.dylib 0x9548da1a NSLinkModule + 92
8 libnspr4.dylib 0x0004a327 pr_LoadViaDyld + 135
9 libnspr4.dylib 0x0004a074 PR_LoadLibraryWithFlags + 228
10 libnspr4.dylib 0x0004a142 PR_LoadLibrary + 50
11 XUL 0x02e68d6c nsLocalFile::Load(PRLibrary**) + 44

hi Simon,

Got the same error message as previous posters. Tried that new link you provided, but Standalone still does not load unfortunately.

I also tried the standalone versions from the Zotero homepage and the link provided above on Mac Leopard. Same crashes...

**************
Process: zotero [12822]
Path: /Applications/Zotero.app/Contents/MacOS/zotero
Identifier: org.zotero.zotero
Version: 2.1.SVN.r7738 (2.1.0)
Code Type: X86 (Native)
Parent Process: launchd [692]

Interval Since Last Report: 146 sec
Crashes Since Last Report: 1
Per-App Interval Since Last Report: 2 sec
Per-App Crashes Since Last Report: 1

Date/Time: 2011-01-19 15:05:51.175 -0500
OS Version: Mac OS X 10.5.8 (9L31a)
Report Version: 6
Anonymous UUID: A39C6156-0933-41B7-8C98-B8557B60DCE1

Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000001578108
Crashed Thread: 0

Thread 0 Crashed:
0 ??? 0x01578108 0 + 22511880
1 ??? 0x01578649 0 + 22513225
2 dyld 0x8fe12f36 ImageLoaderMachO::doModInitFunctions(ImageLoader::LinkContext const&) + 246
3 dyld 0x8fe0e7e3 ImageLoader::recursiveInitialization(ImageLoader::LinkContext const&, unsigned int) + 307
4 dyld 0x8fe0e8c9 ImageLoader::runInitializers(ImageLoader::LinkContext const&) + 57
5 dyld 0x8fe02202 dyld::runInitializers(ImageLoader*) + 34
6 dyld 0x8fe0b64a NSLinkModule + 314
7 libSystem.B.dylib 0x9281fa1a NSLinkModule + 92
8 libnspr4.dylib 0x00043327 PR_LoadLibrary + 535
9 libnspr4.dylib 0x00043074 PR_LoadLibraryWithFlags + 228
10 libnspr4.dylib 0x00043142 PR_LoadLibrary + 50
11 XUL 0x0278ca1c NS_NewNativeLocalFile_P + 3436

**************

Same issue here in OSX 10.5.8. Immediate "application Zotero quit unexpectedly" crash on launch.

Using either the official download of the version posted above by Simon, I get the same error messages others report above.

Specifically, when I check 32-bit mode, I get
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Codes: KERN_INVALID_ADDRESS at 0x0000000001587108.

When I uncheck the 32-bit box, I get
Exception Type: EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000002, 0x0000000000000000.

I just noticed that the standalone download page lists "10.6 or later". Does this mean that there will be no support for Mac 10.5 ever?

Standalone 2.1a3, available now, supports Mac OS X 10.5, but Word integration will not work.

It works for me now as well. Thanks a lot! This will make it easier to convert my colleagues to Zotero.