Well I just bought Portal and I was all excited and stuff so I thought it was great playing it, but then when I got to level 10 (the one with momentum) and finished it, getting onto the elevator, I was going up and then these two orange
things appeared on the side that said something cheat = 1 and something cheat = 0 then it went back to the starting menu... Any ideas on how to fix it would be appreciated.

I looked at the console and it said:

--- Missing Vgui material vgui/BitmapImagePanel
Dropped IIIIIIIIIII from server (Disconnect by user.)
Loading game from SAVE\autosave.sav...
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_-1265_152_256
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_-1952_128_-503
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_-713_64_352
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_640_128_512
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_358_48_368
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_1216_128_488
env_cubemap used on world geometry without rebuilding map. . ignoring: maps/testchmb_a_06/concrete/observationwall_001b_870_128_424
Loading game from //MOD/SAVE/testchmb_a_06.HL1...
Redownloading all lightmaps

I think the Valve/Steam forums might be a better place to ask.