Unfortunately, I'm not sure what to recommend - I've never seen this before. Below is the backtrace from the crash logs (they are all the same crash, btw):
Thread 0 Crashed:
0 ? ? ? 0000000000 0 + 0
1 libsystem_kernel.dylib 0x92161b33 mach_vm_protect + 120
2 ? ? ? 0x00254442 0 + 2442306
3 ? ? ? 0x00253b9b 0 + 2440091
4 ? ? ? 0x00253cb9 0 + 2440377
5 dyld 0x8fe66055 dyld::registerAddCallback(void (*)(mach_header const*, long)) + 109
6 libdyld.dylib 0x9007b078 _dyld_register_func_for_add_image + 74
7 ? ? ? 0x00253a89 0 + 2439817
8 ? ? ? 0x0025204f 0 + 2433103
As you can see there is no mention of Yummy FTP code anywhere here... it doesn't even reach the entry point of the Yummy FTP code before it crashes! If any Yummy FTP code was accessed you'd see com.yummysoftware.yummy-ftp in the second column.
So, the OS is crashing loading an app. Great OS upgrade Apple! ...

Try re-installing Yummy. Maybe it got corrupted? It's a long shot, I have to admit.
Otherwise, re-installing 10.7 might be the fix - it could be a 10.7.1 issue.
I will post this crash log on the developer forums to see if any Apple engineers can help with a diagnosis and/or fix. For certain, though, this isn't a Yummy FTP bug if it never even reaches the Yummy FTP code.