There's a bug in the Tabular Indent Style's Day View. In DAY_EVENT, the creator has misspelt 'weak' several times, using %%color:week_text%%.
This is causing difficulty for some users whose colours schemes lead to the default text colour (since %%color:week_text%% evaluates to nothing, there is no colour change) clashing in some way with the background (%%weak_back%%)
Someone with access to the system account needs to fix this :)</tt>