Error XQE-GEN-0002 JVMVRFY012 stack shape inconsistent;

[patton]

Hi all,

I am dealing with a strange error in my report ( in a union query (Q7) to be exact that calculates the differences between two other queries that are also a union each) like in the diagram
                             Q1
                Q3  ----
                 |            Q2
Q7---U------
                 |           Q4
                Q6 ----
                             Q5


Q3 and Q6 work without an error and so did Q7, untill there was a server restart and all of a sudden when Q7 is ran, this error pops out

XQE-GEN-0002
         An unexpected exception occurred:
JVMVRFY012 stack shape inconsistent; class=com/cognos/xqe/runtree/relational/XUnion$XUnionResultSet, method=getTabularIterator()Lcom/cognos/xqe/resultset/interfaces/ITabularIterator;, pc=10

I've tried recreating the union, but it still shows the error. All other queries work fine, but when I union 2 queries that are unioned previously, I get this error. Tried a server restart, no luck. Any help would be appreciated.