link problems with precompiled headers and boost libs?

Hi, I'm using the datetime library of boost 1_30_0 with VC7.1 with precompiled headers on. We're getting the following link warnings/errors: om.lib(bg_extra.obj) : warning LNK4006: ___@@_PchSym_@00@UwvevolknvmgUtnkEPozhgUhlfixvUytPzwwOlyq@ already defined in om.lib(bg_init.obj); second definition ignored om.lib(bg_extra.obj) : error LNK2005: ___@@_PchSym_@00@UwvevolknvmgUtnkEPozhgUhlfixvUytPzwwOlyq@ already defined in om.lib(bg_init.obj) We include boost headers in our own header files. Our own headerfiles are then used to create a precompiled header. It seems that all object files that use the precompiled header get these link errors... Does anyone know the reason/ a solution for this error? Thanks a lot!