cannot use portableapps at work

Hello, I'm hoping someone can help me. I've installed portable thunderbird on my usb keychain drive and can run it with no problems at home on all computers, even with limited accounts.

However once I take it to work, it spits a few errors at me, then stops reading the drive and thunderbird never starts. I've even put portable Trillian from Trilliananywhere.com on it and a couple of other portable apps from around the web and it's not just thunderbird that's failing.

I suspect it's some sort of security issue with my IT folks at work. What makes me suspect this more is that if I actually copy the folders to my local machine, they run...

So my question is, how do I run these apps directly from my usb keychain drive? It's stupid to have to copy the files to my local computer just to run them.

My usb keychain drive is a 1GB Lexar drive that I converted to NTFS filesystem. I checked it out and it has full read/write access too. So that convinces me even more that it has something to do with some security settings on my workstation at work.

Oh, btw, we use roaming profiles too, not local accounts.

Thanks to any who can help.