I've been installing quite a few of those Linksys/Cisco switches lately, and have an excellent experience with them so far.
Today, I have 2x of them in my Jeep, to go install on a network to replace some DLink DES 32 port switches, one of which started crashing a lot recently. Funny thing is, this existing network has quite a few clone built computers with that (Ugh) Via Rhine 2 adapter....I'm pushing this client to replace those machines as quickly as possible. Soyo motherboards I think. In the past, I've run across issues with these Via NICs.
I don't remember what firmware is the latest...I'll post when I'm onsite, but is yours up to date?
The giga-cable uplinking the two, is it CAT 5e or CAT 6 or CAT 7? Home made or factory made?
Any cables home made? Or all factory made?
Switches on battery backup?
Adequate ventilation? Under full load, they're not stuffed in some cramped area overheating?
You changed the default LAN IP of one of the switches, correct? So they're not both the same IP.
Disable MAC ageing?