calender won't sync 2-way anymore

[lautje2]

Since a few weeks the calender just stopped syncing the calender (wireless) 2-way.
From pc to phone is no problem, but the calender items from phone to pc doesn't work anymore.
it's starting to create problems for me with more appointments at the same time or forgetting appointments.

I tried resetting, changing/storing/checking settings, but nothing seems to work.

any ideas? it's driving me crazy!