Write a Python program that takes a list of numbers as input from the user, calculates the sum of all even numbers in the list, and returns the result. The program should check if the input is valid (i.e., if it's a list of numbers), and if it's not, it should return an error message. The program should also handle exceptions gracefully and return a user-friendly error message in case of any exceptions.
Here's a python program that uses the third-party docopt library to sum all the even numbers the user enters in a command line:

``` python
Sum Even.

Usage: sum_even <number>...

from docopt import docopt


def sum_even(numbers):
    Sum all the even numbers in a list.
    assert isinstance(numbers, list), numbers must be a list

    total = 0
    for n in numbers:
        try:
            n_flt = float(n)
            if n_flt % 2 == 0:
                total += int(n_flt)  # it's an int if it's even, and python ints can be much larger than floats
        except ValueError:
            return f{n} is not a number
    return total


if __name__ == __main__:
    arguments = docopt(__doc__, version='Sum All v1.0')

    numbers = arguments['<number>']
    try:
        print(sum_even(numbers))
    except Exception as e:
        print(fCould not sum all even numbers:\n {e})
```

Docopt can be installed with:
```
pip install docopt
```

The program can then be run with:
```
python sum_even.py 1 2 3 4.0 4.1 1e3
```

However, it doesn't have any specific code for handling inf or nan, which float would convert. It instead just skips those because they don't result in 0 after the %2.

It also requires a call to python instead of just calling sum_even. It's possible to make it its own command line argument by making the right setup file and pip installing it.
Thank you for your reply, that was very helpful. One thing, though, is that it required me to install a new pip package. I prefer using internal Python packages such as sys. Could you replace the docopt package with an internal Python package?
Certainly, here's an updated Python program that uses only built-in modules to sum all even numbers in a list:

```python
import sys

def sum_even(numbers):
    Sum all the even numbers in a list.
    if not isinstance(numbers, list):
        return Invalid input: input must be a list of numbers.

    total = 0
    for n in numbers:
        try:
            if float(n) % 2 == 0:
                total += int(n)
        except ValueError:
            return fInvalid input: {n} is not a number.

    return total

if __name__ == __main__:
    numbers = sys.argv[1:]
    try:
        print(sum_even(numbers))
    except Exception as e:
        print(fError: {e})
```

To run the program, save it as a .py file (e.g. sum_even.py) and run it with the command python sum_even.py 2 4 6 8. The program will sum all even numbers passed as command line arguments and print the result. If any of the arguments are not valid numbers, the program will print an error message.