[IE] Floated fall out of the container div

I'm experiencing a bizarre float problem with my layout in IE/Windows. It concerns this website.

To make it more clear I'll give a small introduction on the layout.

- One container div, #outer, positioned relative to center everything horizontally.
- 3 main divs, #hdr, #bodyblock, #ftr, floated left. Except for #ftr, which is clear: both.
- The upper divs (the navigation etc) are of ne importance, they are simply positioned absolute in the #hdr div.
- For #bodyblock I created 3 columns. #col_links, #home en #col_rechts.
- The left- (#col_links) and right column (#col_rechts) each contain respectively 2 and 3 divs, which also contain 2 divs.
- The footer (#ftr) is being cleared with clear: both.

I colored the right column (#col_rechts) organge the visualise the problem. The upper container div in the right column (#lid_worden) works perfectly. The 2 following container divs (#leden_login and #nieuwsbrief) seam to fall out the right column (#col_rechts). The linkk in #lid_worden (>> inschrijven), the upper container div in the right column, also falls out the right column, though it has the background color of the right column (#col_rechts).

Who can tell me what goes wrong here, and how I can fix this nasty problem?