I downloaded the full IRIS MiG 29 package & IrisMig29-sp2Upd-1.zip from your first link to check this out. I found the update contains a lot of unnecessary files which makes it rather confusing. Try pasting a copy of vc_glass.bmp from one of the texture.navyxxx folders in the update into every texture folder in your MiG 29. That should fix it.

PS. I'm assuming you have FSX + SP2.