I am not using exchange, just pop and smtp. I receive the error whenever sending or receiving attachments over 90 KB. I have created a new .pst, tried different smtp's, uninstalled my internet security. I have no problems with attachments using the webmail clients. I have also installed thunderbird and everything works as it should. This is only happening in Outlook 2007. The problems began about a month ago after running fine for 3 months.
Windows 7 64bit ultimate