Gmail is intermittently flaky. In fact, for a period of about 3 weeks, last month, my 6 gmail accounts were hardly push. For whatever reason, they work almost perfectly now.
I tried everything, including calling verizon and trying to get tech support from google, nothing seemed to work, except waiting it out.
However, I have noticed just a TAD bit more flakyness over the last week.
You can try deleting the account from BIS and adding it again, but in my experience it tends to do nothing at all (at least when dealing with gmail.)
Why can't google just offer the same level of service as yahoo seems to?