Problemas ao anexar docx

Estou com um problema na minha aplicação para anexar específicamente arquivos do office 2007, outros arquivos, anexam normalmente. Alguem já passou por um problema parecido antes?

Obrigado.

Aqui vai uma lista das extensões e seus respectivos Mime Types.

Por exemplo, se antes .doc => application/msword, agora .docx => application/vnd.openxmlformats-officedocument.wordprocessingml.document

.docm,application/vnd.ms-word.document.macroEnabled.12
.docx,application/vnd.openxmlformats-officedocument.wordprocessingml.document
.dotm,application/vnd.ms-word.template.macroEnabled.12
.dotx,application/vnd.openxmlformats-officedocument.wordprocessingml.template
.potm,application/vnd.ms-powerpoint.template.macroEnabled.12
.potx,application/vnd.openxmlformats-officedocument.presentationml.template
.ppam,application/vnd.ms-powerpoint.addin.macroEnabled.12
.ppsm,application/vnd.ms-powerpoint.slideshow.macroEnabled.12
.ppsx,application/vnd.openxmlformats-officedocument.presentationml.slideshow
.pptm,application/vnd.ms-powerpoint.presentation.macroEnabled.12
.pptx,application/vnd.openxmlformats-officedocument.presentationml.presentation
.xlam,application/vnd.ms-excel.addin.macroEnabled.12
.xlsb,application/vnd.ms-excel.sheet.binary.macroEnabled.12
.xlsm,application/vnd.ms-excel.sheet.macroEnabled.12
.xlsx,application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
.xltm,application/vnd.ms-excel.template.macroEnabled.12
.xltx,application/vnd.openxmlformats-officedocument.spreadsheetml.template