Dashboard gadgets use ajax/rest requests. Internet Explorer incorrectly caches these and so sometimes data shown on dashboard is outdated. This bug is stricly related to IE, it works correctly in Firefox and Chrome.

e.g.: You just closed a task a go back to dashboard. In the filter however the issue is still showing.

Possible fixes:
Append all ajax/rest urls with a unique parameter e.g. &uniqueTime=<miliseconds sice epoch> .
Or make all ajax/rest requests pragma: no-cache (if IE works with this correctly)