The dominant culture often sets the standards of what are considered "normal" behaviours or practices in the workplace, and people from various subcultures are often underestimated, not because their work is bad, but because they do not behave in expected manners.
For example, in Navajo culture, looking someone directly in the eyes is considered rude. In many eastern cultures as well, it is inappropriate, especially for women, to look directly at powerful males outside their immediate families. In the workplace, this might be read suggesting dishonesty or lack of personal confidence rather than as simply a cultural difference in body language.
Another issue is religious observances. For example, orthodox Jews cannot work on the Sabbath and Muslims need to pray at five specific times a day. Taking time off for these activities can be regarded negatively by the dominant culture.
Often cultural differences, such as attitudes towards time or standards of politeness, can cause tension between members of different cultures in the workplace.