stupid gdb question "Cannot access memory at address 0xXXXXXXXX"

I've just installed gdb ('opkg update ; opkg install gdb') but it will not
allow me to examine memory:

(gdb) x /8xw 0x48050440
0x48050440: Cannot access memory at address 0x48050440

And this behavior does not seem to be a function of the memory address I
choose. I'm new to gdb and I'm guessing that I'm missing something simple.
Has anyone else encountered this?

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