Texture lighting transitions with cubemaps

First of all: Sorry, I?m using probably the wrong terms for lightning reflexions and stuff..

This is my problem: The floor in my (first) Map is composed by multible solits but all these solits have the same texture on it (hey, its one floor). After placing the cubemaps (perhaps somebody could tell me in which interval to build them in, whats a good distance, besides) in each room, compiling and "buildcubemaps" there floor reflects great BUT the transitions from one texture to the next looks sloppy. You can see where the transition is because the reflection breaks and another starts.

Look here to see what I mean:

What you see here is the transition from a floor-solid in a dark area to the floor-solid of the room next door. You can see where the new texture begins...

If i would set the (now) dark solid as the floor in the hole corridor, the same effect would occur at the door...

The question(s): Does anybody know how to reduce or abolish the effect? Does it have something to do with the cubemap-setting and can it be fixed by optimizing the setting?

Please help me, Obiwan! You are my last hope.

You might want to
look
here where Jeff Lane commented on a similar problem someone was
having.

Essentially, you can force certain brush faces to use a particular
cubemap, so you don't see a seam between faces that use different
cubemaps.

Yeah, I tried this also but, if you do so, bigger faces-reflektion especially those with more than one light-source look, as if they are not properly enlighted. I still hope someone has another advice, but thanks so far!