ive been getting this problem for over a week now, i didn't renew my supporter status until its sorted as i wasn't sure how long it would take me to come up with the fix.
SO far I have tried all of the following and it hasn't worked (HOWEVER, it could work for other users):
-Deled the Jagexcache folders:
C:\USERhere\.jagex_Cache.32
C:\.jagex_Cache.32
C:\Users\nathan\jagexcache\jagexlauncher\bin
Unstalled & reinstalled Java, Runemate & oldschool.
1. Uninstall all 3 (delete cache first)
2. Restart
3. Reinstall all 3
4. Restart again
5. Done.
None of those worked for me but they worked for me in the past when i encountered this problem. If anyone knows any other solutions or possible fixes please let me know.