When an overweight item is stored in inventory it can be grabbed and deployed on the ground. Though, it cannot be put back due to mass limit check.

Seems like it only affects some MKV USI colonization parts. Here's some screenshots illustrating the problem http://imgur.com/a/epxNI

For the bug to show up the part needs to be heavier than EVA kerbals can handle. E.g. for one kerbal it's one ton. As long as wet mass of the component is less than 1t there is no problems.