Here's a fix that worked for me:
Within the carrington-blog theme directory, I edited the file css/ie.css this way:
How it was, before the changes:
/* IE doesn't comprehend the short-notation override */
#navigation ul,
#all-categories ul {list-style-image: none;}
How it is right now, after the changes, where it works for me:
/* IE doesn't comprehend the short-notation override */
#navigation ul,
#all-categories ul {list-style-image: none;}
#navigation li:hover {position: static;}
#all-categories li:hover {position: static;}
The "navigation" line applies to the main menu behaviour, and the "all-categories" line applies to the categories menu behaviour.
Hope it helps!