Little issue with Properties Menu?
First off, let me introduce myself. I'm Brandon and I've been interested in Portal for well over a year now (pre-ordered it the Orange Box so I had it the day it came out) and after beating the game, like just about everyone else here... I just HAD to make levels!
I have mild experience with editors like UnrealEd and I've used 3D Studio Max and Photoshop in the past. A few weeks ago though, marked my first time ever having opened up the Source SDK... ever. 
Now that you all know who I am, heres my problem.
When I create a brush, by default it's a physical matter that the player and objects collide with. The outline of a level.
When I tie this brush to an entity though, this brush can then act as a "trigger_multiple" (triggers events when something touches it), "func_door" (opens and closes like a door and be used as a parent), etc.
After I tie a brush to an entity and set all of it's properties, I click Apply and then X or Cancel. Everything is still well and good.
My problem though is, getting back into those properties. Sometimes when I try to get back into the properties menu, it'll show me the properties of the brush (door speed and direction for a func_door for example), but other times when I go into the properties, it will act as if it was just a normal brush that wasn't tied to an entity.
Left is what I want. Right is what I don't want.
I don't really know the whole pattern to this, and I wish I did because it's starting to really bug me. It happens even when I restart Hammer.
Any idea's? I'd really appreciate it. Thanks!
Firstly, welcome to the site Brandon 
Can't say I've experienced your problem, as far as I am aware its not possible to un-tie the entity (someone correct me if I'm wrong here).
So really I'm not at all sure what is happening, perhaps you can post a map it is doing it on?
Once it has 'lost' the entity does it ever come back?
I'm with the cake:
First, welcome. Always good to have a new mapper around.
Secondly, no... there is no way to un-tie an entity. Once its an entity... theres no going back (except for undo, possibly) that I know of. The closest you can go back to a regular brush would be func_detail, which would still have the same property menu you are looking for. My only guess would be you're forgetting to hit Apply sometimes, but I've never encountered anything like this.
Thirdly, yes, you can un-tie an entity. Simple select it, then hit tools>Move to world, or click ToWorld under the vigroups window.
Oddly, I found i had this problem with my func_door when creating my.. door.. strangely enough.
In the end i had to make the whole function in one go, or else it would lose all it's properties if i closed the window.
You just keep on trying till you run out of cake!?
In the end i had to make the whole function in one go, or else it would lose all it's properties if i closed the window.
you know the small button with IG on it... have it not selected, it doesent only ignore groups it also ignores entitys
WOOT COMPETITION
Make sure the "ignore groups" selection feature is turned off.
thats what i said
WOOT COMPETITION
Good to know, the amount of times I've wanted to untie and ended up remaking the brush 
And it worked! Thank you!
Next problem though, I tried getting into my Portal SDK for Source SDK, but it wont stop changing back to Half-Life 2. It lets me into "Half-Life 2 Episode One" which I don't even have installed, but for some reason it will not let me select "PortalSDK" anymore.