DOS uses location $45 when converting your decimal numeric parameters to hexadecimal for its internal use. Similarly, the monitor's interrupt handler uses $45 to save the 6502 accumulator. So, if an interrupt occurs while DOS is executing a command, the numeric parameters DOS uses when it executes commands are changed. Also vulnerable is the sector length of the files listed in a catalog, since DOS also uses $45 to display this length.
Since DOS uses timing loops during its read and write operation, interrupting the Read Write Track Sector routines can kill a disk. DOS protects itself from IRQ, but has no control over NMI (nonmaskable interupt)--so don't use a NMI while using DOS.