To “Trash the Preferences” – https://www.steinberg.net/en/support/knowledgebase_new/show_details/kb_show/removing-the-preferences-of-the-sequencer/kb_back/2025.html?tx_p77sbknowledgebase_pi1[keyword_search]=Preferences
Jack 
PS: A Tascam US-1641 is a USB 2.0 interface 