Do you have filemaker advanced? You could turn on the Script Debugger mode.
Piggybacking on MikeD's suggestion...
You can also recover the file (FILE > RECOVER) using the Advanced Recover Options and choose to bypass the startup script which would allow you access to the file to either delete the script or modify it appropriately.
I thought I read somewhere that CTRL+SHIFT while opening will disable the startup script.
Pressing Esc on Windows or Command-.(period) on Mac will abort the script if you have "Allow User Abort" off. Close Filemaker first then reopen the file. That will buy you a little more time to press the keys.
I did what Mike said and used the debugger to edit the script and that did it for me thanks for all the orker solutions though, might come in handy later down the line
As a side-note though, the programmees of this website website should really work on this site, I spent like 20 minutes trying to reply in Mac safari before I logged in on my iPhone and wrote the reply there, and my god how slow everything is aswell.
But, I got my answer so I'm happy with that, again, thanks