Issue is fairly straightforward. When evaluating a D code block that includes a table var, this error is thrown by the DMD compiler.
~\Temp\babel-1032v-N\C-src-1032Xig.d(25): Error: cannot implicitly convert expression (row) of type ulong to uint
Failed: ["dmd", "-v", "-o-", "~/Temp/babel-1032v-N/C-src-1032Xig.d", "-I~/Local/Temp/babel-1032v-N"]
The type `ulong` is not appropriate for the generated code, as it represents an array index. The fix is to change line 434 in ob-C.el from:
"string %s_h (ulong row, string col) { return %s[row][get_column_num(%s_header,col)]; }"
"string %s_h (size_t row, string col) { return %s[row][get_column_num(%s_header,col)]; }"