Howdy All:
I tried to Mantis this, but for some reason when I tried to commit the post, it would always tell me "document contains no data". Is that Mantis' way of saying I'm too long-winded or that the image I was including was too big?
Anyway, I'll post this here. I've been having this problem with FS2 for as long as I can remember... even way back in Retail, though considerably less frequently. For this reason, I'm sure I'm not the only person to ever encouter this, but I haven't seen any posts regarding it so I'll continue. First, here's the image:

Note the vertical color bars that have entirely taken over one of the nebula background (.pcx) images, the similar effect on the Orion textures with partial tranlucency (you can see though the ship), and the same effect with some of the HUD. For the HUD, note that I've blurred the directives, ship names and class designations, for campaign secrecy. This bug usualy happens when a mission has many background textures and is very dynamic. This kind of thing is quite common for me in full nebula missions, which is quite annoying. Pretty much anything that uses a textures is subject to this bug, but sometimes I can go through a mission with only one nebula texture being affacted and nothing else. The only way I've found to correct this bug, is to pause the game, alt-tab to the desktop, then return to the game and resume. This will reset the affected textures, but it won't prevent the problem from occuring again. If not corrected in this fashion, more textures are likely to screw up in this manner.
I searched Mantis for any similar posts (under keyword "graphics") but the closest thing I found was a reference in bug147. Also, I have encountered bug147 (assuming I'm understanding the account correctly) and I've found that my corrective action from the color bar texture bug (pause, alt-tab, return, resume) seems to do the trick for this as well.
This bug seems more common under HTL, though I started using Lightspeed's new 32-bit TGA graphics around the same time, so it may be the increased system strain caused by the them and not HTL.
My system specs are:
AMD-800 (200 bus)
256MB SDRAM-133
ASUS V7100 GF2MX 32MB AGP, any drivers
WinME
Later!