Session cookies being deleted without being coded to do so

This is very frustrating.

On development, it is working with no problems, whatsoever.

On staging (as it probably will on production), here is what it's doing:

If "expand all" is clicked, this is the cookie value:

Code:

---

vddstatus
cat1,1|cat2,1|cat3,1|cat4,1|cat5,1|cat6,1|cat7,1|cat8,1|cat9,1
domain.com/
1088
1060073856
33063389
2884050624
30125481

---

If "hide all" is clicked, this is the cookie value:

Code:

---

vddstatus
cat1,0|cat2,0|cat3,0|cat4,0|cat5,0|cat6,0|cat7,0|cat8,0|cat9,0
domain.com/
1088
1060073856
33063389
2884050624
30125481

---

If any individual "hide" or "expand" is clicked, this is the cookie value:

Code:

---

vddstatus
TLTUID=29A2C6BA180E1018889AF39A9D19E869
domain.com/
1088
1060073856
33063389
1613223328
30125482

---

Not only can I not see what is causing this to happen, but the fact that it is NOT doing this in development is really driving me up a wall. It's the same code on both servers.

Any ideas?

^_^