Yes, doing the full reset (CTRL+@) can help. Possibly, you've got corrupt data in the lower RAM, and BASIC is trying to do something there and getting a problem.
Does MONITOR seem to work? If it does, then you need to look at the code around DFD1 and DFD6, and see what it's trying to do. I'm pretty sure that these addresses are within the BASIC ROM code, and they are prob setting things up in the lower RAM area.
A, B and X (indeX) are the registers, C is the Status reg, S is the Stack Pointer and P is the program counter.
At this moment, the next memory address is DFD6, so the prog may be trying to do DFD4. Interested to know what value is in DFD1.
Further looking in my manual says that ROM area D000-DFFF is for Menu, Monitor and virtual screen routines, so the values you show may merely reflect the 'Trap' code.
Again, does MONITOR word. Does this allow the usual D command to Dump memory contents. Addresses 00 - 4D are I/O ports and should be 'Protected'. If you try to access them, does it say 'Protected'? Do you get normal Dump for addresses past 4D?
Geoff