Wrong transfer of attributes to render tree, in case of rendering ICE strands, when using rasterizer for primary rays. Issue is already described in this thread.
It never happens with XSI 7.01, with Softimage 2010 it happens sometimes, with more than 10000 points per cloud. With SI 2011, it seems it appears all the time, when count of points is more than around 2200.

Because I didn't played with SI 2011 yet, and I got this info from another people, here is a simple setup done with factory nodes only, that can cause this issue. Create a grid, go to Simulate>ICE>Emit Particles From Selection, delete simulation region in stack, set rate to about 3000 per frame, set Particle shape to segment, set Rasterizer for primary rays.

Cheers

Okey after I found out that the problem I had rendering strands I googled for a solution and found this thread...
In Softimage 2011 SP1 the same bug is still in there, no fix.

I reported this to support, and it seems to have been fixed in the SAP release

Really ?
THIS would be awesome.

Just tried the 2011 SP1 Hotfix but same issue

I just checked again, SP1 with hotfix still has the bug, SAP doesn't

here's the repro steps I sent to support
To reproduce:
* Load XSI_SAMPLES/Scenes/ICE/Particle_Strands_Seaweed.scn, open the bottom ice tree of the cloud
* In "Emit from Surface", set "Shape" to "Segment", Rate to 3000, Size to 2 (pixels)
* Plug a "Randomize Color" into "Color" param of "Emit from Surface"
* Edit "Scene Material", connect an "Attribute_Color" to surface, set "Attribute" to "Color", disconnect the rest
* Now if you zoom in to the tips of the strands and open a Render Region, you'll notice the OpenGL and the rendered output have the same color
* Switch the Render Region to "Rasterizer", and you'll notice that the colors changes

What exactly is SAP ?
Is it the 2011.5 subscription package ?
Because right now my company only has 2011 SP1, but if I can be sure with the newest version the problem is fixed we will update.

Yes it's Subscription Advantage Pack (2011.5)
I'll increase strand count really high and check again, but I'm pretty sure it's fixed

Ok I found no way to reproduce this bug in the SAP release, even with very high strand counts and toggling back and forth Rasterizer/Scanline/Raytracing.
The bug is easy to reproduce with all earlier versions of Softimage.

Well, it doesn't happen in v7.01 too. Almost all strand renders that I did, had some attribute transfer, or many of them - even 3d vectors for 'bump-mapping'. All were done with rasterizer.
Nice it's working again in SAP.