Django. user_id null & duplicate error - django

Question

Django 1.3
Python 2.7
In fixing one error, I've developed another. I'm not even sure where to begin, I'm so frustrated.
I got my app to show up in the Django admin section, and when I click on "add", it brings up the form. When I fill it out & submit it, it results in this error:
Exception Value: (1048, "Column 'user_id' cannot be null")
Seems simple & clear, but if I add user_id to my admin.py, then it results in the error I just fixed. If I leave it out and use the code that fixes the old error, then I get this error. Here's the relevant code:
admin.py (I commented out the code I was using, as that caused the earlier error)
from timeslip.models import Timeslip
from django.contrib import admin
class TimeslipAdmin(admin.ModelAdmin):
pass
#fields = ['user_id','day','hours_as_sec','part_of_day','drove','gas_money','notes']
admin.site.register(Timeslip, TimeslipAdmin)
models.py
from django.db import models
from django.contrib.auth.models import User
# Create your models here.
class Timeslip(models.Model):
user=models.ManyToManyField(User)
day = models.DateField()
hours_as_sec = models.PositiveIntegerField()
part_of_day = models.CharField(max_length=16,choices=PART_O_DAY)
drove = models.BooleanField(default=False)
gas_money = models.DecimalField(max_digits=5,decimal_places=2)
notes = models.TextField()
class UserProfile(models.Model):
user = models.ForeignKey(User)
url = models.URLField("Website", blank=True)
position = models.CharField(max_length=50, blank=True)
User.profile = property(lambda u: UserProfile.objects.get_or_create(user=u)[0])
If I make Timeslip's user=, into a ForeignKey(User) instead of a ManyToManyField(User), the error becomes:
Exception Value: (1062, "Duplicate entry '2' for key 'user_id'")
...which I understand, but that's exactly what I'm trying to do here now -- make multiple timeslips for each user.
How do I do that? I keep getting ridiculous errors no matter what I try, and it's hard finding documentation on this even though it seems like it would be a common & basic thing.
Update:
New question. Is Django caching stuff? I removed something from the model and reset everything but it still shows the old form. If it's showing me something it cached - How do I flush that cache?
Anyway, here's the output when I run manage.py sqlall timeslip
BEGIN;
CREATE TABLE `timeslip_timeslip` (
`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
`user_id` integer NOT NULL,
`day` date NOT NULL,
`hours_as_sec` integer UNSIGNED NOT NULL,
`part_of_day` varchar(16) NOT NULL,
`drove` bool NOT NULL,
`gas_money` numeric(5, 2) NOT NULL,
`notes` longtext NOT NULL
)
;
ALTER TABLE `timeslip_timeslip` ADD CONSTRAINT `user_id_refs_id_bb29929c` FOREIGN KEY (`user_id`) REFERENCES `auth_user` (`id`);
CREATE TABLE `timeslip_userprofile_user` (
`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
`userprofile_id` integer NOT NULL,
`user_id` integer NOT NULL,
UNIQUE (`userprofile_id`, `user_id`)
)
;
ALTER TABLE `timeslip_userprofile_user` ADD CONSTRAINT `user_id_refs_id_c73880a3` FOREIGN KEY (`user_id`) REFERENCES `auth_user` (`id`);
CREATE TABLE `timeslip_userprofile` (
`id` integer AUTO_INCREMENT NOT NULL PRIMARY KEY,
`url` varchar(200) NOT NULL,
`company` varchar(50) NOT NULL
)
;
ALTER TABLE `timeslip_userprofile_user` ADD CONSTRAINT `userprofile_id_refs_id_d05b8c80` FOREIGN KEY (`userprofile_id`) REFERENCES `timeslip_userprofile` (`id`);
CREATE INDEX `timeslip_timeslip_fbfc09f1` ON `timeslip_timeslip` (`user_id`);
COMMIT;