After starting up Fallout 3, the green arrow and DarN UI indicator don't show up and the game freezes, with the music playing, but I am forced to reboot. Usually this is something wrong with mod incompatibilities, but I got those sorted out way back in March. I haven't made any changes to F3 (aside from updating the Mothership Zeta Crew mod) since March, and I recently upgraded to Win7. Here's my load order:

[X] Fallout3.esm
[X] Anchorage.esm
[X] ThePitt.esm
[X] StreetLights.esm
[X] BrokenSteel.esm
[X] PointLookout.esm
[X] Zeta.esm
[X] Unofficial Fallout 3 Patch.esm
[X] Destruction.esm
[X] Impervious Power Armour.esm
[X] CRAFT.esm
[X] CALIBR.esm
[X] xCALIBR.esm
[X] xCALIBRuniverse.esm
[X] Project Beauty.esm
[X] Mothership Crew.esm
[X] TSC Air Support.esm
[X] EVE.esm
[X] FO3 Wanderers Edition - Main File.esm
[X] Mart's Mutant Mod.esm
[X] Enhanced Weather - Rain and Snow.esm
[X] EnclaveCommander-OA-Pitt-Steel.esm
[X] DCInteriors_ComboEdition.esm
[X] RH_IRONSIGHTS.esm
[X] MyMansion.esp
[X] Sydney Follower.esp
[X] aHUD.esm
[X] iHUD.esm
[X] Unofficial Fallout 3 Patch - Operation Anchorage.esp
[X] Unofficial Fallout 3 Patch - The Pitt.esp
[X] Unofficial Fallout 3 Patch - Broken Steel.esp
[X] Unofficial Fallout 3 Patch - Point Lookout.esp
[X] Unofficial Fallout 3 Patch - Mothership Zeta.esp
[X] DarNifiedUIF3.esp
[X] Project Beauty- Broken Steel.esp
[X] Project Beauty- Point Lookout.esp
[X] TakingOutTheTrash.esp
[X] TOTTPointLookoutEdition.esp
[X] CASM.esp
[X] RH_IronSights_Basic_VanillaPlugin.esp
[X] RH_IronSights_Basic_AnchoragePlugin.esp
[X] RH_IronSights_Basic_PittPlugin.esp
[X] RH_IronSights_Basic_PointLookoutPlugin.esp
[X] RH_IronSights_Basic_ZetaPlugin.esp
[X] RH_IronSights_Pitt_NewRifleSights.esp
[X] RH_IronSights_RemoveReticule.esp
[X] RH_IronSights_PL_NewItems.esp
[X] Feng Shui.esp
[X] GalaxyNewsRadio100[M].esp
[X] UPP - Pack 1.esp
[X] UPP - Pack 2.esp
[X] UPP - Original Perks.esp
[X] UPP - Experience Perks.esp
[X] UPP - Quest Perks.esp
[X] UPP - Beverage Perks.esp
[X] Destruction - Main.esp
[X] Destruction - Main - Statics.esp
[X] Destruction - DLC.esp
[X] Destruction - DLC - Statics.esp
[X] Megaton House and Theme Overhaul.esp
[X] FO3 Wanderers Edition - Main File.esp
[X] FO3 Wanderers Edition - DLC Anchorage.esp
[X] FO3 Wanderers Edition - DLC The Pitt.esp
[X] FO3 Wanderers Edition - DLC Broken Steel.esp
[X] FO3 Wanderers Edition - DLC Point Lookout.esp
[X] FO3 Wanderers Edition - DLC Mothership Zeta.esp
[X] FO3 Wanderers Edition - Followers Enhanced (BrokenSteel).esp
[X] FO3 Wanderers Edition - Project Beauty.esp
[X] FO3 Wanderers Edition - Project Beauty (Followers Enhanced).esp
[X] RH_FWE_Patch.esp
[X] WeaponModKits.esp
[X] WeaponModKits - FWE Master Release.esp
[X] WeaponModKits - OperationAnchorage.esp
[X] WeaponModKits - ThePitt.esp
[X] WeaponModKits - BrokenSteel.esp
[X] WeaponModKits - PointLookout.esp
[X] WeaponModKits - Zeta.esp
[X] AsharasBatmanItems.esp
[X] ZL-ACR.esp
[X] ColtM4Carbines_RHIronSights.esp
[X] ZL-MP5 Pack.esp
[X] 3EFdrg.esp
[X] Dragonskin Tactical Outfit.esp
[X] DragonskinBonusPack.esp
[X] sunglassescollection.esp
[X] Slof's Alsatian Dogmeat.esp
[X] Gunfire Sound Range Increased.esp
[X] EVE.esp
[X] EVE Operation Anchorage.esp
[X] EVE - FWE Master Release.esp
[X] EVE - FWE Master Release (Follower Enhanced).esp
[X] EVE Anchorage - FWE DLC Anchorage.esp
[X] EVE - FWE with WeaponModKits.esp
[X] Mart's Mutant Mod.esp
[X] Mart's Mutant Mod - DLC Anchorage.esp
[X] Mart's Mutant Mod - DLC The Pitt.esp
[X] Mart's Mutant Mod - DLC Broken Steel.esp
[X] Mart's Mutant Mod - DLC Point Lookout.esp
[X] Mart's Mutant Mod - DLC Zeta.esp
[X] Mart's Mutant Mod - Master Menu Module.esp
[X] Mart's Mutant Mod - Project Beauty.esp
[X] Mart's Mutant Mod - FWE Master Release.esp
[X] Mart's Mutant Mod - FWE Master Release + DLCs.esp
[X] Mart's Mutant Mod - FWE Master Release + Project Beauty.esp
[X] 1PipboyPDA.esp
[X] TSC Air Support.esp
[X] Aim Toggle.esp
[X] Fellout-pipboylight.esp
[X] Enhanced Weather - Rain and Snow in Fallout.esp
[X] Enhanced Weather - Weather Sounds in Interiors.esp
[X] Enhanced Weather - Sneak Bonus during Storms.esp
[X] Fellout-Full.esp
[X] Fellout-Anchorage.esp
[X] Fellout-BrokenSteel.esp
[X] Fellout-PointLookout.esp
[X] Fellout-Zeta.esp
[X] Destruction - CP - Fellout.esp
[X] xCALIBRuniverse.esp
[X] xCALIBRUniverse - WMK.esp
[X] RH_IronSights_Vanilla_NewWeapons.esp
[X] Sydney Follower - FWE Dialog Fix.esp
[X] Remove That Glove.esp
[X] 1alexscorpionsnipergear.esp
[X] 1jeansandshirt.esp
[X] The Mall OverHaul.esp
[X] M1911.esp
[X] drc_FatManUltra.esp
[X] New Slower Degradation.esp
[X] MyMansion_FastTravelIndoors.esp
[X] KnockYourselfOut.esp
[X] Sydney Follower - Project Beauty Appearance - Custom Hair.esp
[X] M14_EBR.esp
[X] BrokenSteelFix-GNRAnnouncements.esp
[X] Bobbleheads.esp
[X] FalconPunch.esp
[X] TenpennyGhoulsAtPeace.esp
[X] Sydney Follower - Load Order Fix.esp
[X] Bashed Patch, 0.esp

This happens to me sometimes as well.

When you start the game, DO NOT do any input, e.g. moving the mouse or pressing any keys, and after a few seconds the DarnUI symbol in the bottom-left of the screen will pop up. After that, you can skip the opening credits and proceed normally.
That works for me, anyways. Let me know if it helps.

Note that on my game, if any input is done before the DarnUI symbol appears, the game will completely freeze and the only way I can exit is with ctrl+alt+del.