[theOZer]

kyle1745,
Thread Thumbnails in (your selected) forums works in all vB38x versions so far. You should not need to make any changes/tweaks to this mod's base thread thumbnails plugin after a vB update.
To display thread thumbnails in your Search lists and/or your Tags list you need to tweak search.php and/or tags.php (like we have had to for all previous vB version updates since 368).
If you have the 'Thread Thumbnail - Search' plugin turned ON - Did you change, add the TT code to the vB3.8.x search.php file? (see Post # 112 on Page 8 or do a Search this Mod looking for search.php, whatever)
If you have the 'Thread Thumbnail - Tag Search' plugin turned ON - Did you change, add the TT code to the vB3.8.x tags.php file? (see Post # 169 on page 12 or do a Search this Mod looking for tags.php, whatever)
In my testvb instance I successfully upgraded to vB3.8.x, after adding the TT code to both search.php and tags.php, and both plugins work for me.
~theOZer